Thursday, 20 September 2018

FLYING HEAVY ....

Acknowledgements: Thomas P. Turner (Mastery Flight Training Inc.)

heavily loaded airplane is usually loaded further toward the aft end of the envelope than many pilots are used to. Passengers and baggage that make up the extra weight which drives the gross weight upward are usually added to the aft part of the cabin, moving the centre of gravity (CG) toward the aft end of the weight and balance envelope.

Even 
within the approved envelope, compared to a more forward CG condition, for any given indicated airspeed the aft-loaded airplane will: 
  • tend to pitch upward more
  • fly at a higher angle of attack 
  • be less stable in pitch (tend to nose up and down, and not maintain a given attitude) 
  • take less force on the elevator to change the pitch attitude, or conversely, respond more dramatically to the same amount of control input

The rearward CG limit of an aircraft is determined largely by considerations of stability. The original airworthiness requirements for a type certificate specify that an aircraft in flight at a certain speed dampens out vertical displacement of the nose within a certain number of oscillations. 

An aircraft loaded too far rearward may not do this. Instead, when the nose is momentarily pulled up, it may alternately climb and dive, becoming steeper with each oscillation. This instability is not only uncomfortable to occupants, but it could even become dangerous by making the aircraft unmanageable under certain conditions.

When entering a 
landing flare in an airplane loaded toward the aft end of its envelope, if the pilot applies the same amount of aft elevator control he/she is conditioned to add, the result will be a greater nose-up pitch and a higher angle of attack. The airplane will tend to flare high; it may stall and “drop in” for a hard landing.

Such a flare often results in one of three outcomes:
  1. The airplane hits hard on the main landing gear, possibly blowing the tires or damaging the gear and causing the airplane to go out of control on the runway.
  2. The stall occurs high enough above the ground that the nose drops far enough for the nose gear to hit the ground first. The nose gear collapses and the pilot may or may not lose directional control.
  3. Either attempting to correct for the stall or after initial impact with the ground, the pilot enters a Pilot-Induced Oscillation - that is exacerbated by the stability effects of aft CG and quickly increases in amplitude until the nose gear collapses and/or the pilot loses directional control. 

Most flight traininoccurs with two persons on board and somewhere between half-full and completely full fuel tanks. Unless you’re in a Cessna 152 or a J-3 Cub or similar, this is a fairly light airplane weight with the centre of gravity near the forward edge of the envelope.

Your experience with take-offs, landings, go-arounds, stalls and other high angle of attack manoeuvres, then, is usually under the best conditions of stability and handling your aircraft can provide. If the airplane has a high useful load capability and/or a wide centre of gravity rangethe airplane’s stability and control response in common accident scenarios may be very different from those which you encounter in training

Very frequently, hard landings and airport-environment Loss of Control – Inflight (LOC-I) involve a heavily-loaded airplane and/or one in which the CG is toward the aft end of the envelope.  Your conditioned response to these scenarios, reinforced in practice and instruction, may not be adequate for recovery from performance excursions under these conditions.

Perhaps we should all carefully load our aircraft near the aft end of its CG envelope at the airplane’s maximum weight, and with 
an instructor experienced and current in that type of airplane go up and practice slow flight, stalls, go-arounds, and high performance (short- and soft-field) take-offs and landings in this condition. If your airplane is one that has a large rearward movement of the centre of gravity with fuel burn, you might also practice these manoeuvres at lighter weights but with the CG near the aft limit.

Performing this exercise does three things for you:
  1. It refreshes you on the process of computing aircraft weight and balance. My experience is that very few pilots feel confident in making a loading calculation. This suggests that they rarely do so and are less likely to know when their airplane is loaded at the edges of the envelope - or even outside it
  2. You’ll gain an appreciation for the changes in airplane stability, performance and handling across its entire range of approved loading 
  3. You’ll be better practised and ready for a high-performance take-off and landing, go-arounds and stall recoveries in conditions more typical of the way you may routinely fly your airplane … conditions less represented by the way you’ve been trained and evaluated on these skills

Ask your instructor to help you train for common LOC-I scenarios, and to avoid hard landings, by experiencing them at weights and load distributions more typical of how you fly the airplane. It might be a good focus of your next Flight Review or other training event.

FLY SAFE!


Monday, 10 September 2018

THINGS ARE NOT ALWAYS AS THEY SEEM.........

Acknowledgements: Rod Machado

(Ed. Note: An interesting technique for anyone experiencing difficulty in touching down gently ….)

“When I was a very young flight instructor in the right seat of a Cessna 210, I witnessed a very unusual behaviour. The fellow I observed looked like he was performing miniature push-ups on the yoke, moving the elevator forward and aft in small increments during the landing flare. It appeared that he was pumping himself up to get down, and he continued these shenanigans until the wheels kissed the concrete below.

Stranger than the act was the action. While doing his routine, and despite the forward and aft elevator movement, I hardly felt the airplane pitch up or down, nor did I feel his subsequent smooth landing. Equally remarkable was the fact that his landings were consistently smooth nearly every time I flew with him.

What was 210 Man doing here? Why would someone push and pull on the elevator control during the landing? And why would this behaviour result in little or no pitch acceleration during the flare, much less a smooth touchdown? The answer lies with a concept I later came to call the threshold of immediate control.

One of the reasons pilots have difficulty making smooth landings is their failure to anticipate and compensate for ground effect during the flare. As an airplane approaches the runway surface, the wing’s downwash on the tail decreases, resulting in the nose pitching forward. The manner in which downwash affects the airplane is sometimes irregular and inconsistent, making it difficult to anticipate, much less control, the downward-pitching nose.

It’s as if the downward pitch of the nose sneaks up on a pilot and doesn’t allow much time for reaction. The result is often a series of over- and under-corrections and eventually a hard landing. If it were possible to compensate for the change in downwash by a linear increase in back pressure on the yoke, pilots would land more smoothly more consistently, because most of us routinely attempt to pull back steadily on the yoke as we flare. That’s what we were taught to do. But there’s nothing linear about elevator control forces during the flare, especially when flying larger single-engine airplanes.

There are many variables affecting the rate and degree to which the nose pitches forward in these conditions (weight, C.G., aircraft type, control surface size, and perhaps phases of the moon). To compensate for these variables (and make smoother landings as a result), 210 Man manipulated the yoke with small back and forth movements. His constant probing let him find the sweet spot where any further pull would cause the nose to rise and any less would cause it to fall. He was on the threshold of immediate control.

His technique prevented the natural forward pitching of the nose from catching him unaware. By manipulating the flight controls in this way, he knew precisely when to pull aft on the elevator and the precise amount of pressure with which to pull to maintain the desired closure rate with the runway.

To better understand this technique, here’s another way of looking at how you can apply it.

After the round-out and during the flare, apply continuous elevator back pressure, but do so in small pull-and-release motions. Think about pulling just far enough aft so that the nose would rise beyond the desired pitch if you pulled even a tiny bit more. As you begin to release a tiny bit of elevator pull, you’ll find a point where the nose would drop with any additional release of pressure. You’ve arrived at the threshold of immediate control. But the threshold is always moving, so you have to keep testing. It’s the constant recalibration resulting from this pull-release motion that allows you to make the airplane’s nose stay right where you want it to stay, and lets you retain immediate control of the airplane’s attitude. This means that the airplane’s nose shouldn’t unsuspectingly pitch downward without your being able to immediately stop its motion.
Now, you’d think the plane would be jumping up and down like one of those mechanical bulls in a Texas bar. The pull-release motions, however, are small enough (if they’re done correctly) that no one in the cockpit will feel any vertical pitch acceleration. This is especially true in heavier single-engine airplanes, where small elevator movements don’t result in the airplane’s immediate vertical acceleration. On the other hand, the lighter the airplane the more immediate will be the vertical acceleration from even small elevator movements.

The proper application of this technique requires proportionally smaller forward and aft yoke movements to remain in the threshold of immediate control when flying airplanes in the weight class of a Cessna 150 or J-3 Cub.

Despite the lack of pitch acceleration, you’ll still see the controls moving forward and aft during the flare. That’s what propelled my eyebrows when observing 210 Man many years ago. This movement doesn’t matter as long as the airplane isn’t pitching up and down and annoying anyone on board. Remember, there are many ways to fly an airplane, and this is just one technique to help some pilots make smoother landings.

Over the years, I’ve observed this technique being used by pilots who I suspect had experienced a decline in their kinetic, visual or tactile sense (perhaps because they counted sunspots for recreation and/or manicured their fingernails with power tools). It took me a while to realize that what they were really doing was amplifying their sense of elevator response. In this way, they were seldom surprised by a sudden change in attitude because they were continuously making micro control adjustments on the yoke and thus compensating for the tail’s aerodynamic surrender as it neared the runway.

As an aside, this pull-release technique is often used by pilots making extreme short field landings. Pilots operate deep in the region of reversed command during these landings. Slight forward and aft movement on the elevator lets them know how much (if any) aft elevator travel is still available, as well as how effective the elevator response is at that instant. The moment the elevator hits the stops, the pilots knows he’s reached the limit of the pitch envelope and must now compensate with a change of power or forward pitch.

By practising with the threshold of immediate control during a few landings, you will gain a better idea of how best to flare your airplane. I’ve used this strategy successfully with students transitioning to larger machines, where the stick forces are noticeably heavier throughout the flare.

Ideally, you should apply one continuous increasing pull on the elevator during landing. As you get to know your airplane by using the pull-release technique, you’ll be in a better position to approach the ideal.

Or not. Some people have a difficult time making landings any way other than pull-release. So be it. While it may look a bit strange to a close observer or new flight instructor, at least they’ll land as softly as a butterfly with sore feet".

FLY SAFE!

DON’T TURN A PRACTICE EMERGENCY INTO A REAL EMERGENCY

DON’T TURN A PRACTICE EMERGENCY INTO A REAL EMERGENCY

Acknowledgements:  AIR FACTS/Tom Curran

“I was out at my local airport one recent afternoon, watching planes beat up (or should I say pulverize), the traffic pattern, and I saw something that really made me wonder what folks were thinking. 

I observed one locally-based Cessna 172 try to execute a simulated engine-out emergency landing on our 5,000 ft-long runway. I could see that there were two people in the airplane, but I can’t say for sure that it involved a CFI giving dual instruction.

They flew a very tight base-to-final turn, and were still pretty high over the threshold; I’d estimate around 200-300 ft AGL.

The winds were light, and it looked like they had partial flaps extended. Since they were obviously going to land very long, and really did have power available, I was betting they would abort this attempt and try it again.

I was a bit surprised when they continued their descent to the runway. (Hmmm… Maybe they really do have a problem…) I don’t remember seeing anything that looked like full-flaps coming down, but they appeared to try a fairly weak attempt at a forward slip when they got down to maybe 100 ft.

By this time, they were way past mid-field, and I could just barely see them over the curve of the earth (I was sitting adjacent to the approach end). I’m guessing they landed about 4000 feet down the runway.  So, I was even more surprised when they executed a touch-and-go out of it!

“So what?” you may ask; “A 172 can get airborne in less than 1000 feet.”  That’s not the point. The point is: Don’t create a possible real emergency situation while simulating an emergency.  If you’re doing engine-out landings, give yourself a reasonable distance to put it down on the runway; after all, you’re practicing for a possible worst-case scenario of having to land in a very small, tight, confined space. 

If you’re not going to make it, penalize yourself by going around (which we also need to practice), and trying it again, and again, and again, as necessary.  If you have a real emergency, and end up with 5000 ft of runway available – great!

Continuing that approach to a touch-and-go served no purpose, except to put that crew in peril if their touch-and-go didn’t go as expected”.

FLY SAFE!

Sunday, 2 September 2018

THE MIDDLE-AGED AVIATOR .....

Acknowledgments: Rod Machado

(Ed. Note: For any of you who might be wondering whether or not it could be time to quit ..... it's not inevitable, and Rod provides some psychological food for thought to help you deal with any uncertainty)

“Over the years, I’ve heard many stories about middle-aged pilots (45-65 years) who gave up flying due to a sudden onset of anxiety. Apparently not induced by any specific aviation trauma, nor inspired by the relatively small and perfectly normal decline of reflexes and mental agility experienced by most middle aged pilots. What in the world might spook a 50-ish pilot into abandoning something he obviously once loved to do?

First, let me make it clear that there are probably many answers to this question, but I’d suggest that the most likely cause has something to do with the emotional baggage a pilot accumulates with age. I’m speaking of baggage caused by an unhealthy focus on a pilot’s own mortality, which may result from obsessing over aviation accident data - although there are no doubt many other causes as well.

By the time a pilot reaches the age of 50, he’s been around long enough to hear or read about several of the ordinary and imaginative ways aviators have employed to vaporise themselves in an airplane. For convenience, let’s call this information the dark side of aviation. Long term exposure to the dark side often assaults the mind, lays siege to the emotions and spooks an otherwise mentally healthy pilot. Whatever desire someone has for living a long, healthy life now collides with the memories of those unfortunate pilots who didn’t achieve one.

While clock time is still technically on the middle-aged pilot’s side, he or she no longer feels this advantage. Instead, flying becomes a game of chance, rather than the practical management of risk that it is. At this point some pilots begin to slowly re-evaluate,  perhaps over a period of years, the desire to fly. For others, it’s as if they wake up one day and out of the blue decide they no longer want to soar into it. The net result is an exit strategy that resembles how an engineer behaves when accidentally stumbling into a coffee shop hosting a poetry reading. It may look voluntary, but it's essentially coercedby anxiety.

A pilot surrendering to these emotions is essentially letting the deceased determine how he or she lives. Inasmuch as the NTSB conservatively estimates that 75% of accidents are due to pilot error, we know that fate didn’t hunt at least three-quarters of the pilots involved in aviation’s dark side events (the percentage of pilot-error-type-accidents is really much, much higher). The suggestion here is that these unfortunate pilots made a choice, and they chose wrong.

So what’s an older pilot to do when mortality-induced anxiety compels him or her to question the desire to fly? I’d argue that a good answer is as simple as deciding to have a little more self-faith , and belief in his or her ability to choose wisely in the air.

There’s a very good basis for such faith, too. Living to middle age has to count for something in terms of the wisdom a pilot accumulates. Unlike King Lear in Shakespeare's famous play, few people grow old without growing wise. Surely Bob 5.0 is nothing like Bob 2.0. The later version of Bob better understands his strengths and weaknesses, as well as how human nature affects  behaviour. This is the knowledge that makes us wise, is it not? 

For example, an awareness of human nature may make Bob aware of his desire to please his passengers at the cost of aviation safety. Wise man that he has become, Bob 5.0 now elects to protect himself by obtaining his passengers’ agreement to cancel the flight and reschedule for another day if the weather is poor. 

From a flight safety perspective, knowledge of self (wisdom) is worth a hundred times more than what a pilot may know about how airplanes fly (flight experience). Said another way, age-related wisdom can help us avoid situations where we might have to use our superior skill. And that wisdom helps us avoid situations that require superior skill we might not have.

Based on understanding how wisdom confers a cockpit advantage, the middle-aged pilot with mortality-induced anxiety should find comfort in knowing that he or she’s probably a much safer pilot than he or she allows credit for. As a result, he or she should learn to trust both self and the ability to fly safely as a means of combating his anxiety. 

Is the answer really as simple as that? Consider that, from a cognitive perspective, learning to trust oneself is as solid a therapeutic concept as are the drugs used to treat physical illness. So, yes, the answer can be that simple.

To be clear here, I’m not suggesting that wisdom always trumps the age-related decreases in a pilot’s physical and/or cognitive performance. In fact, some middle age pilots are anxious because they know they’re less skilled than they once were. Wise pilots that they are, they'll most likely opt to fly within the range of their performance limits. Perhaps they'll sell that twin Cessna and opt for a Cessna 182 instead. In this article, I'm speaking only of how a capable middle-aged pilot might overcome mortality-induced anxiety by simply placing more faith in self and ability.

If you’re one of these middle aged pilots suffering from anxiety induced by aviation’s dark side, then isn’t it better to just learn the lessons offered by fallen aviators, instead of bringing the deceased with you on every flight? Let them rest in peace, so you yourself may find greater peace in flight”.

 FLY SAFE!

THE RUNWAY BEHIND YOU…

Acknowledgements: AIR FACTS Jules Tapper)

This is a story about two words – “unfortunately” and “fortunately” – and has been de-identified in order to protect the embarrassed. However much can be learnt from the following incident.

It had been a hot and busy day. The pilot was a diesel and electrical engineer and a specialist on installation and repair of electric power generators in remote areas.

The job was done so it was back to the plane and a quick onload and lash down of his heavy toolbox. The Cherokee 235 was lightly fuelled and, with only the pilot and his toolbox on board, one would think it would have performance to spare.

Unfortunately, the pilot was a big feller, well over 100 kilograms,  and his toolbox probably weighed nearly as much. Fortunately, the airstrip was firm, over 600 metres [1968 feet] in length, the day not too hot, and a windsock down the far end indicated a slight headwind at that point. Take-off performance would be quite good.

He knew the aircraft well, having operated in and out of some quite restricted spaces over quite a long period. No need to taxi back right to the end of the strip – half way up will do! Unfortunately, a bad decision in retrospect.

The throttle was advanced and the aircraft accelerated quickly down the strip and out towards the nearby lake. What the pilot did not realise until he had passed his accelerate/stop point was that the wind, although indicating on his nose at the far end, was in fact hitting a curved ridge just abeam his proposed rotate point, and was curling back down and partially across the strip – giving him a slightly downwind component.

This was “a case of the biter bit”, but there was no means of stopping it. At the last moment and in desperation (as a collision with the fence seemed inevitable), and with very little airspeed showing on the ASI, the pilot reefed on full flap.

Fortunately, the instantaneous increase in lift generated carried the aircraft over the fence and sagging just above the stall into the next paddock. The pilot heaved a sigh of relief as he milked the flap away while staggering away in ground effect.

Unfortunatelywith his nose high attitude, he did not see a cattle beast right in front of him. With a huge impact, his propeller and one undercarriage leg hit the beast and there was a large thump aft. 

However, the plane was still flying, even if a bit unstable in pitch and with the motor vibrating a bit. The pilot glanced over his shoulder and was horrified to note that most of one side of his tail-plane was missing and with the balance turned upwards like a giant wind-brake.

To his credit, he immediately closed the throttle and crash-landed into the next paddock and slid to a halt. Had he not done so and continued on, the aircraft, as speed built up, would have become undoubtedly unstable and crashed into the lake with little hope for a happy ending. Fortunately, there was not a scratch on the pilot.

Unfortunately, the aircraft was not so lucky. The impact with the cattle beast had bent the prop, torn off one undercarriage leg and wrecked the tail-plane assembly completely as well as doing associated wing and fuselage damage.

So what would an analysis of the incident reveal? The pilot admitted afterwards that, had he known the local characteristics of the strip better and not been in such a hurry, he would have taxied back and used the full length for take-off. He would have bolted away had he done so, as he would probably have been airborne and accelerating quickly when he would have encountered the area of tailwind component. Even if a little sink was encountered, at this point he was still over smooth ground with no obstacles to immediately climb over.

“What happened to the poor old cattle beast?” I hear people ask.Fortunately, it was a quick death. The propeller had cut it clean in half right on the backbone. There was some post-accident humour in the incident however, when the pilot later informed me quite indignantly that he had of course to pay a substantial amount as an insurance excess incurred for subsequent repairs to his plane, plus a pay-out on the third party damage (the beast), but that he had not been offered even a little portion of the meat that was dressed out from the departed animal.

And the moral of the story?

·      On take-off, remember that the runway behind you is of no use to you. Take all you can – you never know when you will need to use the lot.
·      Learn from the mistakes of others… There is no truth in the motto “Al audaz fortuna favorece” (Fortune favours the bold ) when it comes to aviation safety.


FLY SAFE!