How To Land

I’m flirting with the idea of writing shorter articles with more plain language rather than my usual 4 to 5 page descriptions of obscure aerodynamic theories. So in order to make this work, I’ll just pick either a common question or an interesting fact to expand upon. If you see me go past a page or two, feel free to yell at me.

 

How to land a light airplane.

airplane, landing, central jersey regional, piper warrior, aviation

Landing is actually easy in theory. Unfortunately, things like crosswinds, visual illusions, weight and balance changes, and the use (or non-use) of power make it far more complex in reality. In the happy and easy theory world, the basic to-do list is comprised of lining up with the runway, picking a spot you’d like to land just beyond and aiming the nose roughly at it, flying towards it and finally, slowly raising the nose right before touchdown. As you can see, there are a lot steps and the introduction of variables to each will make your job harder. But I know you can handle anything so lets go step by step:

Line-Up:

Lining up with the runway means making sure that your airplane’s path is drawing a line from the center of the close-end of the runway through the center of the far-end of the runway. If there is a crosswind, your nose may be pointed some other direction. Just focus on your groundtrack (your actual path) rather than your heading (where you’re facing). If there isn’t a crosswind, this part will consist of rolling out of a turn aligned with the runway centerline and making small adjustments to stay there.

Picking A Spot:

For years, fighter jets had a display called a velocity vector that was a representation of where there airplane would end up if its energy state didn’t change. When projected onto a head-up display, one could simply place the velocity vector onto the desired touchdown area and make sure it stayed there. Now, many general aviation aircraft have glass panels that feature the same technology. But before you start staring at panels, learn how to do the same thing visually. Find a spot on the runway that’s just a bit short of where you’d actually like to touchdown. Trim the airplane for final approach speed and try to keep that aiming point at the same spot over the nose. If the spot moves up without the nose changing pitch, it means you’re getting low. If the spot moves down, you’re getting high.

Flying To It:

Your final approach may require power. Don’t get so hung up on terms like “glideslope” or “glidepath” that you refuse to add power and end up coming in too low and hitting a tree, or telephone pole, or some kid’s kite (well, these days it’d probably be a “drone”). Keep your airspeed within a couple knots of the approach speed you require. If it’s gusty, the old rule of thumb is to add half the gust value to give yourself a cushion in case of a sudden change in windspeed or direction. Glance at the panel over to make sure important things like flaps and landing gear are where they should be. Oh, and make sure you’re landing on the correct runway. This can be embarrassing and/or dangerous depending on the situation.

Raising The Nose:

The flare is the part of landing that often gives students trouble. Simply stated, the flare is when the pilot brings the nose from a shallow descent back up to level flight. Some instructors will say “Raise the nose in the flare”, which usually results in the most likely nervous student overcontrolling and lifting the airplane back up into the air rather than settling to the runway. Today, a lot of instructors prefer to tell students to instead “Bring the nose to level”. Some will extend that further and say “Bring the nose to level and don’t let the airplane land”. The last instruction is what helped me improve my landings to a much higher standard. By holding the nose level a foot or two off the ground, the airplane will begin to decelerate. As it does, it will want to sink. To stop it from sinking, squeeze back a little more on the controls to try to hold altitude. The increase in pitch will create more drag, which will increase sinkrate, which will cause you to squeeze back more, ad infinitum. After a few seconds, the airplane will be out of energy and gently touchdown on the main gear. The closer you are to 1.3 times the stall speed in landing configuration, the less you’ll float past your aim point (which is why you purposely aimed a little bit short in the first place).

Some new students will get worried they’re going to slam into the ground and flare way too high, leaving the aircraft and the state of their laundry in a precarious position. The flare will be performed lower than you might expect. If you’re having trouble estimating height, try quickly glancing out the side window to get some depth perception. Staring straight ahead tends to leave you with few cues on how high you are. If you are uncomfortable in slow flight a foot off the ground, have your instructor take you to an airport with a long runway. There, you’ll be able to takeoff and instead of climbing out, reduce power and hold it low to get used to what you’ll see and feel just before landing.

 

So there you go. On a calm day you should be able to land a light plane like a pro. Next time I’ll bring up crosswinds and how to deal with those without fanfare.

Piston Propfan Proposal

Traditional Propellers

After a recent bout of studying piston engine aircraft performance, I’ve become convinced that advanced engines are not really necessary for higher cruise speeds. All evidence points towards propeller design as the missing link in light aircraft capabilities. Propellers for the most part have not changed since World War I. The most recent developments have involved scimitar shapes, swept tips and lightweight composite materials. However the basic issue of thrust diminishing with increasing speed has remained an issue. WWIScimitar

An aircraft with a fixed pitch propeller can be thought of as a car with only one gear. Fixed pitch props can be optimized for takeoff, cruise or a mixture of the two. The cruise prop will have lackluster takeoff and climb performance due to its higher pitch. The engine literally doesn’t have the power to spin the prop to its optimum speed at a static condition. Conversely, the takeoff or climb prop will have large amounts of thrust at low speed, but a limited top speed. The hybrid prop is a middle of the road compromise between the two.

High performance aircraft worAvengerHubk around this problem by varying the pitch of their blades to allow for maximum thrust at high RPM situations like takeoff, and maximum efficiency at lower RPM conditions like long-range cruise. This is the aeronautical equivalent of shifting gears in a manual transmission car. A system of flyweights and a governor allows the system to seek the pitch that maintains a selected RPM.

As an aircraft accelerates, all propellers make progressively less thrust, even though the engine is producing increasing amounts of power as the prop unloads. This situation has been considered unavoidable, even though it is very possible that there is a way around this dilemma. In theory, there is a way to achieve this, that is not complex and fairly easy to manufacture. To solve this problem, we will look to high bypass turbofan engines.

 

Turbofan Advantages

In the quest for speed, the piston engine has long been abandoned for turbine engines. With an extremely high power to weight ratio, long times between overhauls and superb performance at high altitudes, any turbine engine can be viewed as superior to a piston engine with regards to speed. Where they do no fare as well is in terms of fuel economy and purchase cost. While a new mid-size piston engine for aircraft will be in the $30,000 range, a small turbine engine can easily run 10 times that price.

Fuel consumption is also high for a pure jet, thus almost all new engines are either turboprop or turbofan variants. In the turboprop, a propeller is driven by the turbine via a reduction gearbox. In a turbofan, a large ducted fan is driven by the turbine. While aerodynamically speaking, they are very similar in operation, there are specific features in design that allow for the turbofan to perform at high subsonic speeds with incredible efficiency. The fact that the massive fan does not require variable pitch, yet produces most of the engine’s thrust from zero airspeed all the way up to Mach 0.90 indicates that their design should be studied in further detail for our purposes.CF6

A close look shows that a fan can be considered a nearly solid disk with slots for air to be pulled through (looking at a turbofan from the front, it is very hard to see behind the blades compared with the ease of looking past the 2 or 3 blades of a propeller). These slots are simply the spaces between the blades and vary based on the blade chord. The blades themselves can range in shape from simple twisted polygons to scimitar shaped with serrations for shockwave control. Blade twist is markedly more severe than the twist featured on a propeller due to the larger operational speed range. The cross-section is normally a circular-arc airfoil optimized for supersonic flow. These factors are important in creating a propeller derivative.

Propfan Ver 2.0?

Compare the fan on a turbofan engine with a traditional propeller. Whereas the fan may have over 30 blades, a propeller will have only 2 or 3. If properly balanced, the fan will operate with far less vibration than the propeller. It will also move a greater mass flow per second due provided that adequate horsepower is available to spin it. A propeller will have a larger diameter for a given thrust level than a similar turbofan. This allows a slower rotational speed, keeping tip speeds subsonic and providing higher propulsive efficiency. Supersonic tip speeds are not a concern for turbofans due to the duct eliminating tip losses. Finally, a fan can recover ram pressure as forward speed increases, whereas a propeller will not.

If we assume that our propeller will be a bolt-on replacement for standard 2 and 3 blade props, we cannot duct it. It also must not exceed the diameter or weight of the original prop and be simple to maintain. With these constraints in mind, a 6 to 8 blade design will provide a compromise between static thrust, ram recovery, and low enough noise without the issues of balancing that arise with increasing numbers of blades.

Starting with straight blades of roughly equal tip and root chord, we can introduce severe twist to allow the root to operate un-stalled at very high forward velocities at a rotational speed of around 2500 RPM, which is an average operating range for a piston engine. To ensure that noise is kept to acceptable levels, the blades must be curved and swept to reduce diameter without a commensurate loss of blade surface area. The sweep ideally would begin around the midspan of the blade, rather than near the tip as is typically done.

Those who remember the propfan studies of the late 1980s may make the connection that the aforementioned propeller sounds a lot like the UDF demonstrator. Aesthetically this is true but there are several significant differences. A propfan has much higher blade loading, variable pitch and is driven by a turbine. Our design has a relatively low loading, fixed pitch and is driven by a piston engine. The benefits are ease of construction, maintenance, and operation. For existing aircraft, the major advantages will be improved fuel consumption, faster climb rates, higher ceilings, lower noise and longer engine life. Obviously, cleansheet designs will have to be conceived in order to take full advantage of the possibilities.

Concerns

A potential issue with the use of these propellers is the relatively low RPM at takeoff. This reduces the amount of power that the engine can generate. Luckily, most existing aircraft have a narrow enough speed range that plenty of thrust can still be created even at reduced horsepower levels. As designs emerge that have a speed range greater than roughly 300mph, more work will have to be done on optimizing both ends of the speed spectrum.

With normally aspirated engines, a ram effect from the inner section of the propeller will delay loss of power at higher altitudes. Should forced induction through supercharging or turbocharging be used, care should be taken to ensure that dangerously high manifold pressures are not produced, especially at low RPM settings. The use of electronic ignition with variable spark timing is recommended to ensure that the engine remains out of detonation range at all times.

Structural integrity of the blades will be complicated by the compound curvatures. Materials that are resistant to impact, vibration and torsional stress are required for adequate durability and resistance to flight loads. Use of titanium or single crystal materials would provide the required strength at acceptable weights, but at the detriment of increased cost.

Conclusion

All of this is theoretical and has not been proven other than basic research and back-of-the-napkin sketches. Considering that experimental propfans were able to achieve a 30% reduction in fuel consumption over existing turbofans, the concept does hold merit. Our design may provide a similar boost to existing piston aircraft, but only if the thrust per horsepower ratio is improved over traditional propellers. Testing will begin with experimenting via computer simulations for the best designs and progress to physical models. Comparing our design to traditional propellers will indicate the potential efficiency gains. From there more complete analysis using the horsepower required and drag force of several common general aviation aircraft can be completed.

GA For The Masses

Like many others, I am acutely aware of the slow (and accelerating) death of general aviation in the United States. I won’t go into all the reasons for this as we’d end up with a 400 page article on everything from Baby Boomers to the aircraft certification process. I would like to bring to light some things that will help the public feel like general aviation is something they can be involved with. Hopefully with larger numbers of people who care about flying, our diagnosis will change to “critical but stable” rather than “who is the next of kin?”.

Don’t take these suggestions personally. If we aren’t honest with ourselves, we can’t help ourselves.

 

Stop trying to make everyone a pilot.

Guilty parties: Pilots, aviation advocacy groups.
Who can help: Pilots, aviation advocacy groups, FBOs, flight schools.

Just because a person likes football does not mean that they can or even should tryout for the Dallas Cowboys. Similarly, just because a person shows a passing interest in airplanes does not mean we should try to coerce them to become a pilot. There are people who love to photograph airplanes but hate being in the air. There are some who like being around fast machines but have no desire to spend thousands of dollars on the license (let alone currency and additional ratings). The enthusiast who enjoys paying for a sightseeing ride may not want instruction but is still helping to keep that aircraft and its operator in business. These people are valuable allies in the effort to keep general aviation a part of the fabric of America. One hundred thousand people who are passionate about aviation but aren’t rated are more effective than ten thousand pilots with similar passion. It’s all a numbers game, especially in Washington D.C..

Instead of telling people how great it is to be a pilot, we should understand that while anyone can like airplanes, taking that extra step to become a pilot for most people is Natalie Flyinga pretty significant leap. Invite those who are open to the idea for rides around the pattern. Don’t teach them anything, just let them enjoy and take in the unique perspective from 1000ft AGL. The experience should be something akin to cruising in a classic convertible on a sunny day. The ambiance would be ruined if the driver suddenly began explaining the construction method used for the valve lifters and the maximum cornering g-force.

Hangar Party

For those who show no interest in going up, let them have fun on the ground. Sponsoring regular open-house BBQs or hangar hang-out events at local airports is a great way to get people to the airport. Take care to see that non-aviators aren’t made to feel like outsiders. Consider a country club or marina; not everyone who goes to those facilities knows how golf or sail. For them, the golf and the boats are a backdrop for social interaction. If we use aircraft as a backdrop to events rather than the centerpiece, it makes the concept of being around airplanes less foreign.

 

Make the airport accessible.

Guilty parties: DHS, airport management, people afraid of their own shadows
Who can help: DHS, airport management, local municipalities, aviation advocacy groups, FBOs, flight schools

After 9/11, many airports went from being a fun place to hang out to a glorified Supermax with runways. Trying to fence off an airport for anti-terrorism purposes is to be polite, pointless and insulting. Maybe lawmakers haven’t noticed but airplanes have a peculiar habit of rising far above the security fence once they take off. A two-dimensional solution for a three-dimensional vehicle leaves a spare dimension of uselessness. Furthermore, I doubt that anyone bent on creating havoc and killing innocent people is really going to be worried about a trespassing rap for jumping a six-foot fence.

The best defense is popularity. Rather than fence off airports, turn them into even more valuable places for commerce and recreation. Recreation? At an airport? Of course! Why wait for a municipality to close an airport and turn it into a park? Make it a park right now. Find regions outside the runway protection zone and install bike/jogging trails complete with mile markers and the occasional water fountain. Create a playground in an empty corner of the field safely away from any operations but close enough for kids to see airplanes. With a steady stream of people using the airport for recreation, it becomes much more difficult for the maladjusted to execute their plot. For those convinced that trails would attract ne’er-do-wells, random placement of security/safety cameras along the trail would allow for monitoring of the perimeter, probably to a higher degree than would be possible without such a park.

The idea of an airport as a commerce center is not radical, but actually a very low risk method to bring regular people in close proximity with aviation. With proximity, uneasiness and fear begin to vanish and understanding takes its place. If there is an abandoned building or hangar, there is little reason why the airport, FAA and governing town can’t come to an agreement to let a non-aviation business operate in that location. For that matter, undeveloped space on or near the airport should be considered for retail or commercial buildings. In an ideal world, any retail space would feature windows that face the runway, aviation artwork or even ATC piped in over the stereo system. But even without those nods to aerospace, it’s a far better solution than letting airport buildings sit in disrepair and disintegrate. Not to mention, the tax revenue generated would be a welcome addition to the governing municipality’s coffers (and thus secure the airport a more stable future).

 

Reduce The Elite Status of Aviation

Guilty parties: Pilots
Who can help: Pilots, aviation advocacy groups

Since the first airplane took to the skies, non-pilots have imagined that it takes nerves of steel, lightning fast reflexes and a better handle on math than Euclid. For the majority of flying, this is simply untrue. Judgment and planning are the difficult parts. Usually that’s where mistakes are made that manifest themselves later in flight. The actual act of flying is really easy provided that the proper motor skills and coordination have been learned. I liken it to throwing a perfect spiral in football. You may be able to explain it with physics and algebra but the best way to learn is to practice under the tutelage of someone experienced. After a while it becomes second nature.

The image that the public has of VFR general aviation flying is wrong on many counts. One thing that remains true however, is that flying is unavoidably expensive and that cannot be changed (at least in the current economic situation). We must acknowledge that barrier and not pretend that flying is an affordable activity for everyone. But in terms of operation, a person by no means has to be a steely eyed missile man in order to fly a Piper Cherokee. We won’t be able to impress people anymore about how hard it is to wrestle the controls on a 5 knot crosswind landing, but there will be many more people who will realize that they have the ability to become a pilot too.

 

Safety. Enough Already.

Guilty parties: All of aviation
Who can help: All of aviation

Aviation has a hazardous streak. There are a lot of things that can go wrong very quickly. Even with backups and training, accidents will happen. That being said, aviation as a culture is so safety obsessive that it frightens people away. Right now I’m looking at an general aviation magazine and a motorcycle magazine that are both sitting in my room. Guess which magazine has more articles on safety despite having a lower number of articles total?

Motorcycle riding has very real hazards associated with it, just like general aviation flying. Yet when you read their periodicals, you don’t see issue aftebike-vs-planer issue featuring discussions about accidents and close calls. They focus on the fun aspects of the hobby while still encouraging responsible riding. Justifying our accident discussions as wanting others to learn from our mistakes is noble but selfish. If we think that pilots are the only ones who look at these magazines, we’re wrong. Many a spouse has seen one too many articles on accident rates and one too many features with the title “There I Was On A Dark And Stormy Night With An Engine On Fire” and decided that their mate was not going to engage in the apparently deadly act of flying small planes. Let’s do our best not to scare off people who want to fly or give fodder to the misinformed who think that “little airplanes are always crashing”. This is not to gloss over the risks involved, but to moderate the rate at which they are exposed to them.

 

 

 
These observations are based on spending time around regular people, pilots, then finding the average between the two. Thinking from the perspective of someone who knows nothing about general aviation, a lot of things about flying can be intimidating. Great strides have been made in making airports more accessible to people other than pilots and there are many cases of airports and cities working together rather than against each other. This is proof that reaching out is more effective than pulling back.

There are a lot of misconceptions about flying and many of them are self-inflicted due to our relative isolation from the general public. We need more people to support general aviation but they won’t show up until they feel welcome. Giant billboards and ad campaigns won’t change anything. Conversely, slightly altering our actions makes every pilot in America an ambassador and every airport a welcome center.

Wing Loading: More Important Than You Think

In 2011 I said “We’ll continue soon with more on wing loading…”.

It’s 2015. I think you can see that I get distracted easily and persistently. In any case, the information I’m about to present to you has not and will not change. Use it to help understand why your airplane does what it does when you leave the boring confines of straight and level, or use it to help you design that superplane you’ve always wanted to build. Off we go into the underrated world of wing loading!

Wing loading and power/thrust loading are the two most telling specifications about an airplane. Most pilots go right to horsepower and start swelling with pride when numbers north of 300hp start appearing. The assumption is that a lot of horsepower equates to a lot of performance. This is a huge misconception. The total horsepower of an airplane is irrelevant unless you have another number to compare it with; the total weight. A 200hp plane that weighs 1500lbs is going to have way better acceleration than a 500hp airplane that grosses 8000lbs.

Likewise, wing size and thus the wing loading is critical for many of the aerodynamics qualities of a given airplane. A highly loaded wing doesn’t always equate to high speed. There is a delicate balance of wing loading and all performance parameters that matter to you. Absolute ceiling, stall speed, takeoff distance , landing distance, cruise speed, ride quality and turn radius are all tied to the wing loading of an aircraft. For our purposes, we’re going to ignore the effects of power/thrust loading and focus only on wing loading for the duration of this discussion. By pretending that adequate power is not an issue, we’ll have the ability to truly see the importance of the wing area to weight ratio.

ANGLE OF ATTACK

For any airplane to fly, there needs to be some positive angle between the wing and the relative wind. The higher the wing loading, the greater this angle of attack will be in 1G flight for the same wing at a particular speed (this is where the FAA safety advisory about heavy, clean and slow airplanes generating strong wakes comes from…more alpha = stronger vortex). One can think of wing loading as an energy budget for the wing. If the loading increases, level flight is going to cost more through either higher speed or increased angle of attack. No matter what, you’ve go to pay for weight.

 

HIGH SPEED

Conventional wisdom says that if I want to fly fast, I should have a small wing. This is not completely true; if I wish to fly fast, I need to have low drag. Wing size is related to speed only through skin friction drag, induced drag and in some cases, wave drag. The size of the wing itself is not the sole determining factor. That being said, it takes some creative airfoil design to allow for a big wing that does not produce large amounts of drag. The aft-loaded airfoils that first saw widespread use on the Boeing 757 and 767 series are examples of this type of design. Even with a relatively low sweep compared to earlier models, they produced far less drag per pound of aircraft even at high subsonic speeds.

 

SLOW SPEED

An assortment of flaps and slats allow this 757-200 to land at very slow speeds for an aircraft of its size.

An assortment of flaps and slats allow this 757-200 to land at very slow speeds for an aircraft of its size.

 

Conventional wisdom also says that if I want to fly slow, I should have a large wing. If the wing does not change shape, this is true. However, a small wing can become a large wing through the use of flaps, slats and slots. These devices change the camber and in the case of slotted flaps, the area of the original wing. Since nothing is free on this planet, the extra lift produced also produces extra drag. During takeoff and landing, the objective is to fly as slow as practical to reduce the amount of runway needed. For this reason, the flap/slat/slot solution is used on almost all airplanes to varying degrees. The best of both worlds is attained at the cost of complexity and cost.

 

RIDE

A small wing is advantageous for ride comfort and structural integrity at high speeds. With the increase in wing loading, gusts and turbulence have less impact on the aircraft due to its higher aerodynamic inertia. The best comparison is a ship cutting through 8 foot waves versus a little canoe being tossed around the same ocean. For an aircraft flying in turbulent regions or at high dynamic pressures (50 feet and the speed o’ heat), alleviating aerodynamic stress is a matter of keeping the plane in one piece. There may be reason to maintain a fairly large wing but create the same lift-curve effects through significant sweeping. An example of this requirement would include low level strike aircraft with a secondary air-to-air mission.

 

TURNING

Aircraft A vs Aircraft B and the difference in turning drag.

Aircraft A vs Aircraft B and the difference in turning drag.

Wing loading is very important during any type of maneuvering but for our discussion, we’ll focus on level turns. The moment an aircraft rolls into a turn, the angle of attack is increased. This creates more drag that has to be overcome with additional power/thrust. Obviously, the lower the angle of attack, the lower the turning drag generated. A low wing loading has the effect of reducing the induced and profile drag created during a turn. Using the chart, compare Aircraft A that requires 2 degrees alpha for level flight compared with Aircraft B that requires 5 degrees. As they both roll into a hard turn that demands an extra 10 degrees of alpha, Aircraft A will be turning with a total of 12 degrees alpha while Aircraft B will be at 15 degrees. It is quite clear which airplane will have the better turn performance with regards to drag.

 

CEILING

Yes, this high aspect ratio glider is efficient, but only at low relative speeds.

Yes, this high aspect ratio glider is efficient, but only at low relative speeds.

The oft repeated maxim is that a long thin wing is best for flying at high altitude. The real variable at play here is wing loading, not necessarily aspect ratio. If a given aircraft requires a large angle of attack in order to generate the necessary lift coefficient, excessive amounts of induced drag will result regardless of the speed. An aircraft designed for low indicated airspeeds will probably have a high aspect ratio wing with minimal sweep while one designed for higher speeds will have some level of sweep and a much lower aspect ratio. Either way, the wing has to have a low enough loading to allow for a reasonable angle of attack.

 

INERTIA

For visualization, imagine a dumbell like you’d find in a gym. Pick up a 5lb weight, hold it up about 2 feet over your other hand and let it go. Chances are you can probably catch it quite easily. If you attempt the same feat with a 25lb weight, the only way to catch it is to let your hand drop down to eliminate the shock of it impacting your hand, if you can hold onto it at all. This is the same inertia effect that wings experience as their loading goes up. For this reason wing loading can be thought of as “inertia loading”. You may experience some of these effects in certain aircraft with highly loaded wings in the form of post-stall gyrations or uncommanded rolls.

 

GA DESIGN

A lot of modern GA wings can thank the P-51 for leading the way for laminar flow airfoil sections and high speed planforms.

A lot of modern GA wings can thank the P-51 for leading the way for laminar flow airfoil sections and high speed planforms.

Modern high-speed general aviation designs often have partial laminar flow, medium to high aspect ratio wings. These wings are very efficient at low angles of attack, resulting in low drag at high cruise speeds. They do have the drawback of less than satisfactory behavior at high angles of attack and post-stall. Usually these foibles are corrected with the use of leading-edge cuffs, vortex generators, and washout. In the case that the problems cannot be rectified totally, the aircraft will have limitations such as “spins prohibited” in the manual. If the aircraft encounters turbulence or maneuvers too hard, the stall margin can easily be exceeded resulting in a departure from controlled flight. How bad this gets depends on the aircraft’s design, center of gravity location, altitude and true airspeed at the time.

 

TRANSPORT DESIGN

Aft loaded “supercritical” airfoils allow commercial aircraft to use mildly swept wings without sacrificing subsonic performance. The airfoils delay shockwave formation on the upper surfaces, effectively raising the critical Mach number to a higher value. For this reason, a large wing is feasible but not often used in practice. Ride comfort and the fact that massive flaps are industry standard all point towards ubiquitous use of a highly loaded, high aspect ratio wing.

If a designer wishes to take advantage of smaller airports, utilize lower V1 and Vref values, and produce less drag at high altitudes (eliminate step climbs), a larger wing may be something to consider. The current trend is to utilize effective aspect ratio devices such as winglets or sharklets. These artificially raise the aspect ratio without actually adding any span to the wing. The result is that aerodynamic performance is improved markedly over much of the envelope, although not by the same degree that a larger wing would provide.

 

FIGHTER/TACTICAL DESIGN

F-4, F-22 and F-15E all with highly swept, low aspect ratio wings.

F-4, F-22 and F-15E all with highly swept, low aspect ratio wings.

The advent of thrust vectoring has made nose-pointing an accurate exercise even down to zero airspeed. This does not negate the need for a well designed wing since not all maneuvers will be able to take advantage of vectoring. For aircraft with a low level strike mission, encountering turbulence at high speed can seriously fatigue the crew and at worst, damage the airframe. A high wing loading, significant sweep or a combination may be required to keep the stresses within limits. For all other regimes of combat, a large wing is desirable for maneuverability, payload carriage, and high altitude performance. Due to the forces sustained during combat maneuvering, a larger wing in this case entails additional chord rather than more span.

 

This is just a short highlight of the importance that wing loading carries (punintentional) for all airplanes. I hope you’re more aware of how critical this number is for everything that you do in the air.

Know It All…Or Not

If I have to repair this in flight, something is beyond horribly wrong.

If I have to repair this in flight, something is beyond horribly wrong.

I punched a fist of joy into the air upon reading Bruce Landsberg’s recent editorial in the February 2014 AOPA Pilot magazine. He addressed the topic of useless knowledge being taught rather than critical overall concepts. I’ve been saying this very same thing for years, but since I don’t have a type rating in the Saturn V, I’m viewed as a dangerous menace to the national airspace system. Thankfully, his article lends credence to my stance that we often focus on useless data in aviation that is of little practical or emergency use. We should be looking at the big picture items with a lot more interest rather than the little details that only impress other pilots or examiners.

While I’d love to claim credit for being a maverick as it relates to the idea of not needing to know everything there is to know about an aircraft, NATOPS was leading the way with this mindset years ago. Anyone who has flown in the US Navy knows that the manuals for aircraft are purposely designed to exclude excess systems information. The only things that are included are things that the pilot either has control over, or any system that can cause a hazard to continued flight (and how that hazard will manifest). The reason is simple: mechanics fix airplanes and pilots fly them. This division of labor is present even in civilian aviation where the FAA makes it a point to tell pilots that save for a few preventative measures; they are not allowed to be a mechanic on their airplane.

I believe this focus on knowing every system in detail is a holdover from the good ole days of aviation (which we simply cannot move on from it seems). Systems were very complex and highly mechanical in nature. All of them were controlled by human beings, hence the plethora of people in the cockpit of vintage airliners. The flight engineer literally made sure all the systems operated the way they were supposed to. The pilots flew and if present, the navigator made sure they didn’t get lost. The crew had to understand their piece of the equation and at least a little bit of the other guy’s in order to pull off the flight.

Fast forward to today where the airplane’s flight engineer is the ECAM that collects and displays information about the status of every system several times per second. You literally don’t need to know much more from an operational standpoint for many systems other than “Is it on?”, “Is it off?”, and “Should it be in that state?” A friend of mine flies a Brazilian-built regional jet and has to memorize the starting and operating temps, abnormal shutdown criteria, and various RPM ranges…for the APU. Meanwhile, the only direct control over this device the pilots have is an Off-On-Start switch, a Stop switch and an emergency fuel shut-off switch (in the event of a fire, overspeed or overtemp, the APU FADEC will automatically command a shutdown). Does it make sense that three switches with a total of five possible selections warrants memorizing the type of compressor, every temperature limit, every RPM limit, and the type of cooling used by the APU?

While it may be interesting information to know, the role of a modern airline pilot is not to play mechanic. It is to fly the aircraft from Point A to Point B. If there is a problem with the aircraft, they write up what isn’t working and if it isn’t on the MEL, continue flying until it can get fixed by the maintenance guys. It’s not about being cavalier, it’s about being efficient with specialized skills. Ask yourself if there is any way for a motivated captain to crawl back to the tailcone in flight (there isn’t since the APU is surrounded by a firewall). Even if they could get back there, what could they do to fix a problem? Last time I checked, airlines don’t hand pilots toolkits with their Jepp revisions. What if more time in review and sim sessions was spent talking about things that are more likely to be encountered in day-to-day operations, rather than the specifics of a component that the pilot will most likely never even see and has limited control over?

Air France 447 is a perfect example of why broad scale knowledge is critical. An aircrew faced with a rare and confusing situation may be spring-loaded to go to a rather complex solution due to the way we train them. Ignoring the control input issues, had the crew been taught to look at the big picture of where is the information coming from, they might have considered the fact that the FMGS was likely showing correct groundspeed based off the GPS signals it automatically updates with. Additionally, the combination of pitch and power for a given flight condition would have led to suspicion that the EFIS PFD was at least partially lying (and thus to look for independent data, such as the FGMS). This is not an indictment of the crew, but a look at how a few seconds to consider the big picture before zeroing in on a smaller picture solution may prevent accidents like this from happening again.

The Air France accident was not the first time a high performance jet was lost at night in the vicinity of thunderstorms due to faulty instruments. A nearly identical situation occurred in a B-58 on February 14th, 1963 when the pitot tube iced up and the pilot began unknowingly following erroneous airspeed data. When the controls felt sloppy and he suspected something was wrong, the pilot cross-referenced with the Machmeter, but this was also giving an incorrect reading. It wasn’t until the pilot asked the navigator (who had an independent pitot system) what the airspeed was that he realized the delta-winged bomber was about to drop out of the sky. The aircraft ended up departing controlled flight and the crew members were forced to eject (see the article “B-58 Hustler” by Jan Tegler in the December 1999 issue of Flight Journal for the entire story). Hopefully with changes in training and multiple-source independent airdata, there won’t be any more accidents like these.

Aerodynamics is another place where we overthink things to the point that it might be causing poor decisions in some situations. My favorite horse to flog is the recent bank angle conservatism being taught in the United States. There is no magic law of aerodynamics that says if you bank 31 degrees at 999 feet AGL, your airplane will autorotate into a flat spin. Although the intentions are good, the source of this fear stems from the g-load charts that we all looked at as student pilots. In a 60 degree bank, load factor is doubled and stall speed increases substantially. The only problem is that this is only true if you attempt to maintain altitude. It is not even close to accurate in a descending turn. Nor is it accurate if one is flying an airplane with a lot of excess power/thrust. We have become so obsessed with the book numbers that the bigger picture of how aircraft actually fly in three dimensions is being lost.

Don't freak out if you hit 60 degrees of bank while descending.

Don’t freak out if you hit 60 degrees of bank while descending.

There are student pilots (and an increasing number of certified pilots) who will either fly C-5A sized patterns, or make skidding turns in order to keep the bank angle low. The former negates the engine-out glide advantage of a close pattern while the latter actually is a perfect setup for a spin. To be honest, a bank beyond roughly 30 degrees is not really necessary at speeds under 80 knots if the proper lateral spacing is used. The trap is when the pilot comes in a lot faster or much closer due to ATC request or their own misjudgment. All of a sudden as they notice they’re going wide, the rudder gets kicked in and opposite aileron starts to hold the bank angle constant. The saving grace is that usually this situation is created by having a surplus of airspeed so a spin isn’t likely provided they return to coordinated flight fairly quickly. Rather than worrying about a chart that isn’t applicable to their conditions, they should be taught the confidence to put the airplane where it needs to be to get where they want to go.

Again, before people get riled up, there is a time and a place for sticking to book numbers. Early 727 pilots who tried to eyeball the landings as if it was a DC-3 with jet engines learned about the importance of sticking to the book. But the book isn’t magic. The numbers it contains are the sum of the properties of the atmosphere plus the aircraft’s design plus the systems installed. If it takes the engines 9 seconds to spool from flight idle to “Oh crap” thrust, the obvious solution is to not be low and slow while at idle. You don’t need to know how many stages are in the low pressure compressor (six total, two fan and four compressor) to get the big picture of why you keep the power up on final. Knowing the big picture of how heavily loaded swept wings behave at high angles of attack will also give you a better understanding of why simply lowering the nose won’t immediately get you out of trouble (plus the delay in thrust buildup to further compound your woes). It is true that sticking to the book will ensure that you arrive safely, but it is better to understand both the concept and the details.

Pilots cannot and should not know it all. The FAA regulation to “Familiarize yourself with all available information concerning that flight” is a rule designed so that if a pilot makes any error that “reckless and careless” doesn’t cover, the book can still be thrown at them. Rest assured that if you put one into the ground a half-mile short, you’re getting blamed for not getting a weather briefing despite it being CAVU with calm winds, flying an aircraft with an inoperative ADF and for not knowing the airport manager’s office phone number . This is a poor way to ensure safety but a great way to have instant blame in the event of an incident. Instead of scaring pilots into trying to read everything to fit some liability model, we should be encouraging them to select the appropriate data for what they want to do.

We collectively have to accept that despite what we would like to have everyone believe, 99.2% of pilots will never know every single little detail about their airplane. This should be instilled in student pilots via the way they are taught. Start with the basics and allow them to get used to the 3rd dimension. Instead of filling their heads with regulations from day one, ease off and let them enjoy flying. Let them have a few hours of wrapping their heads around controlling the airplane before revealing that they’re going to have to become a lawyer as well to understand all the regulations. Instructors can easily move from the big picture of “Let’s do our maneuvers up high so if you make a mistake we have plenty of room.” to the verbatim description of FAR 91.303 over the course of their training. The rules will make more sense anyway if a little bit of experience and common sense are applied rather than “you need to know this for the test”.

As usual, I’m sure not many people will read this (especially this far down) and those that do think I’m either full of myself, dangerous, a crusader or a combination of the three. The truth is I love aviation but I’m also willing to point to where we can do a better job making it less daunting for newcomers to get involved, safer for those already flying and more enjoyable for everyone. If we are honest, it’s time to admit that the act of flying is not very difficult in execution. Judgment on the other hand is what kills people. Being able to recite regulations does not stop people from flying into IMC or descending below minimums. Only the proper attitude and respect for the fact that you’re suspended in the air by the laws of physics and aerodynamics will make a person accept their own limits and those of their aircraft. This must be stressed more than any chart, schematic or diagram.

Texas Aircraft Expo

This weekend I stopped by the Texas Aircraft Expo at Addison Airport. Okay, I’ll be honest, I stopped by on Friday but you get the idea. Held at ExecHangar, several manufacturers were represented and a wide variety of aircraft were on display. Everything from the SportCruiser to the Cessna Mustang were available to be examined up close.

One thing people need to understand about airplanes is that one size doesn’t fit all. If you normally fly trips of 400nm, you may occasionally have a trip that is 600nm. That doesn’t mean that you have to buy a plane that can cover 600nm non-stop. If the 400nm airplane is a better value, you’d save more by making the odd fuel stop for a long trip. It all comes down to smart scaling for your needs.

Below are a few of the aircraft that were on display.

http://eclipseaerospace.net/

Eclipse 500. Can cruise up to 1000nm at speeds over 300 knots.

 

Starting around $3.3 million, the Cessna Mustang cruises around 340 knots and similarly ranges around 1000nm.

Starting around $3.3 million, the Cessna Mustang cruises around 340 knots and similarly ranges around 1000nm.

 

Garmin EFIS dominates the panel with standby gauges and A/P controls at the top of the glareshield.

Garmin EFIS dominates the panel with standby gauges and A/P controls at the top of the glareshield.

A great short field utility aircraft that seats 10 and can be converted to a jump plane, floatplane, or cargo ship.

A great short field utility aircraft that seats 10 and can be converted to a jump plane, floatplane, or cargo ship.

Another turboprop 10 seater, the time tested Caravan is enhanced in the EX version. With a nearly 3600lb useful load, this aircraft can serve a variety of purposes.

Another turboprop 10 seater, the time tested Caravan is enhanced in the EX version. With a nearly 3600lb useful load, this aircraft can serve a variety of purposes.

 

Even the Husky has embraced glass panels as evidenced by this Garmin setup.

Even the Husky has embraced glass panels as evidenced by this Garmin setup.

 

As you can see, there are a lot of aircraft out there to serve the needs of your business. Most if not all of these aircraft are available through shares or fractional ownership. The advantages of this arrangement are having maintenance and overhaul costs included in the monthly rates.

 

Old School Navigation: DIY Visual Approach Charts

In the olden days before the advent of moving map GPS but following the bad old days of the four course, navigation was a mix of pilotage, NDB and VOR tracking. The aircraft I’ve flown recently all have either a large GPS, a glass panel or a combination of both. That doesn’t mean that I always use them as a primary means of getting around. Call me crazy, but looking out the window is a lot more fun than staring at a screen.

I was fortunate to have instructors in my formative years who were old school navigators. They knew how to use GPS like wizards but wouldn’t let me use it until I had figured out how to read a map. After all, the map on the GPS is a repeater of sectionals and enroute charts that pilots used to carry before the iPad was invented. Knowing how to read one means knowing how to read the other. I was taught to look for checkpoints that were not directly under me (or at least offset myself by a 1/2 mile so I could see something prominent), not to draw a course line from the middle of an airport to the middle of another (unless you make a Dutch F-16 style takeoff, or fly out of ADS, not many people turn on course by midfield) and most of all, to verify the correct checkpoint by referencing it with another landmark.

One problem I had in parts of NJ and PA was finding certain airports. I knew where they were based on planning, they just had a pesky tendency to be hidden by trees and hills. We never flew much above 3000 MSL for the obvious airspace reasons, thus my limited line of sight in some areas meant that a few airports didn’t reveal themselves until the last second (at least on the first trip to a new field). Annoyed by this, I started drawing my own visual approach charts and still do to this day. It’s fun and gives you something to work with when flying into an unfamiliar field.

This technique works really well in densely populated areas also, day or night. Usually the airport is the dimmest set of lights out there and it’s hard to resist the urge to focus on a shopping center or highway just beyond the rotating beacon. For the approach into ADS from the north, an easy way to get in is to be north of the Sam Rayburn Tollway and the Dallas North Tollway intersection when you call up Regional Approach. At the southeast corner of this massive intersection is the huge headquarters of Hewlett Packard which actually is a charted VFR checkpoint (formerly Electronic Data Systems, hence the EDS on the chart). Follow the Tollway south and when you pass the next spaghetti-bowl intersection of the George Bush Tollway and the Dallas North Tollway, you are 2.7nm from ADS. Chances are unless you’ve been there before, you won’t see the airport but may see the beacon (it is literally in the middle of a city). Just keep following the Dallas North Tollway. Whoever built it must have been a pilot because at the 45 degree pattern entry point, it turns to you guessed it…a perfect downwind leg for Runway 33. Look to your right and you’ll see the airport if you’re at pattern altitude.

The Addison “Tollway Visual Rwy 33” sets you up for a right downwind entry.

Satellite terrain view of the densely populated North Dallas area and how congested the boundary of Addison is.

Getting back to 47N at night after returning from Long Island was made simple by using a natural landmark. I followed the Raritan River until it literally dumped me out on extended final for Runway 25. Starting You’ll pass over a wide freeway bridge, the NJ Turnpike/I-95. When you pass this bridge, a quick look to your left (south) should reveal the 2 Tower Center, which is as you probably guessed, two tall office buildings. Due west of I-95 is the Rt 1 bridge, followed soon thereafter by a series of highway bridges and a railroad viaduct linking New Brunswick to Highland Park. On the north side of the river at this point is the Rutgers football stadium that occasionally has a TFR but if there are no lights on, there shouldn’t be any issues (NOTAMS or a quick call to NY Approach keeps your conscience clear). Keep going and you’ll see I-287 making an “L” in front of you (and crossing the river). Just after this, the river will curve to the left, you’ll cross I-287 again and when the water becomes difficult to see, look up and you’ll see Runway 25 directly in front of you.

River Visual for Central Jersey Regional Rwy 25.

Satellite terrain map view of approach into Central Jersey Regional showing how the river narrows as the airport is reached.

Nearby 47N is SMQ, which is from some angles hidden by trees. Follow I-287 to the north and when you are parallel to the large Aventis Pharmaceutical facility on the right, look to your left and the airport will be there. If you happen to miss it from this angle, continue north until reaching the juncture of I-287 and I-78. Turn west to follow I-78 and look to your left again. The airport is in the southwest corner of this juncture less than a mile from your position.

Somerset Airport visual approach following I-287 with multiple reference points.

Wider view of the “inital” fix into SMQ.

Going to Newport State, RI? From the west, follow the Jamestown Bridge that crosses Narragansett Bay. When the highway bends sharply to the south, continue to the east. Cross the bay, pass over the Newport Naval Complex and cross highway 114 (north-south orientation) and you’ll be midfield for UUU.

Newport State Bridge approach. Note obstructions on the Newport segment of the bridge.

Wide view of approach over Narragansett Bay and the Naval Facility.

These are just a few of my personal examples and I’m sure you have your own for fields you fly into. The advent of satellite maps online has made it easier to cross-reference ahead of time what the terrain looks like rather than looking at yellow vs tan vs brown on a sectional. Plus the ability to see what buildings are near your destination airport is a vast improvement over trying to guess which warehouse or mall to look for while airborne. While I would rather fly with a moving map as a bright and shiny cross-reference, I have no issues going without one. Planning makes all the difference in being where you want to be vs someplace else. Happy navigating.