AAIB Accident reports

[Chuck Ellsworth]

I have just returned to Canada from London and while I was there I read some AAIB accident reports.

Can anyone tell me why the most common accident with light aircraft is landing on the nose wheel and generally tearing it off?

Cat Driver:

[tacpot]

The topic has been much debated. I know where you are coming from though - having read the AAIB reports for the pass five years, I'd guess there are no more than five months when a C152 didn't have a nose wheel torn off.

On the one hand, the accidents are often (but not always) training accidents, and you would expect more mistakes to be made in training. In the early stages of training an instructor might hold their hand firmly in front of their yoke, to stop their student lowering the nose too much, but at some point the instructor has to let the student do the entire landing, including making corrections themselves, without seeing an expectant hand hovering by. Same goes for the error of not rounding out quickly enough. Perhaps its just a price we have to pay for having trainers that you can't groundloop (easily:) ).

On the other hand, the frequency suggests that something is amiss with the training regime - it also suggests that the problem is not a recent one, nor is the frequency changing very much.

I've not studied the location of the accident reports in detail, from my own training I found (in the early stages) that the 350m runway was not quite long enough to give plenty of time to float the aircraft along the runway until it begun to run out of flying speed (just in case you'd come in too fast - a very common problem, and one that is probably linked with the nose wheel collapse problem). The approach speed control is I think the key to this problem:

You come in too fast, so you have less time to make the transition to level flight, which means less margin for error. Too much speed means the end of the runway is rushing up at you, so you either push it on at high speed (poor nose wheel) or go around and risk your instructor's wrath, plus spend an additional 10 minutes in the pattern to do it again.

What do others think?

[DFC]

Agree that approach speed must be a factor in many cases.

I do not believe in the statement that keeping the speed up is safer. As was correctly pointed out, it simply increasesd the chances of removing the nose wheel.

Another problem which is more common is the use of an approach speed and a threshold speed e.g. "approach at 80 reducing to 70 over the hedge".

I much prefer to make a constant speed stable approach at 1.3 Vso. This provides a safe margin above the stall without requiring a large dumping of inertia in the hold-off and flare.

Finally, I prefer to teach students that the roundout and flare are to reduce the rate of descent...not to stop it.

Thus a steady approach at 1.3Vso which results in a gentle flare which reduces the rate of descent to an acceptible rate and the aircraft landing main wheels first is the best.

Another factor often is the pilot pushing forward on the stick after the aircraft baloons in the flare. The only remedy for this situation is a missed approach. When one looks closer, the reason for the baloon is often excessive speed and moving the column rearwards too quickly in order to arest the descent.

DFC

[Chuck Ellsworth]

From my obversations and discussing landings with pilots it is my beliefe that nose wheel landings result from the pilot being trained to look at the far end of the runway.

In most light aircraft such as Cessnas if you raise the nose to the proper touchdown attitude the end of the runway will disappear due to the nose blocking it.

Therefore a great number of the nose wheel landers have never been taught correct height judgement above the landing surface.

Look along side the nose to judge height as the nose rises and blocks the foward view would be a good start.

[tacpot]

There's another one in August's reports :
http://www.aaib.dft.gov.uk/bulletin/aug02/gbptu.htm

After reading this report. I think the corrective action made during the bounce was wrong. To my mind (and you have to bear in mind that I am a low hours pilot), in the situation described the student as caused the accident by actively doing something to put the nose wheel back on the ground. My instinct would be to pull back (or at least maintain my back pressure) on the control column and let the aircraft settle back on the runway with the nosewheel held off.

(Please understand that I'm not being critical of the student)

So I'm beginning to think that another part of the problem is reinforcing in the student's mind the need to maintain the correct landing attitude when very close to the ground. It sounds obvious but it obviously isn't getting set into student's minds quickly enough to prevent these nose gear collapses.

Chuck's idea about moving the point of focus from the far distance to the near distance is certainly a cause of landing problems, as you can't judge your height off the ground when looking at the far end of the runway. From my own training I can remember the difficulty in making this shift of viewpoint.

I suspect Chuck's analysis is true for Pilots who wheelbarrow the aircraft onto the ground without ever landing on the mains, and mine is true for Pilots who land and then land again, breaking the nose gear on the second attempt. I think there is a link between the height estimation problem and the landing attitude judgement that causes additional accidents on top of those caused by each factor seperately. A complicated problem.

[FormationFlyer]

Yes - correct action is to hold your attitude, maintain the back pressure, possibly add a little power - but never never ever push fwd/release the back pressure until the main wheels are down...if it all goes pear shaped simply go-around...

If you move your gaze to the near part of the runway you still cannot judge height and will flare late...again with the possibility of a balloon & bounce or worse - wheelbarrowing in...

The correct place is at the far end of the runway..but just to the side of the nose...say 10-20deg off the runway...this allows you to judge height...its what we teach for night landings where its really hard to judge height.

Nose gear incidents usually happen because of

1. too late flare
2. incorrect action during bounce
3. trying to find the damn runway - it was there the last time you looked....ask the italian display pilot who did his nosewheel at RIAT this year....a very silly mistake...

[Blue Hauler]

Chuck,

I don’t think instructors bother teaching students where to look ahead during the final approach and round-out. Cessna tail-draggers probably blocked more of the view than most others from their stable. I was always taught to look to the left of the nose, not over it. I teach the same technique and find that it encourages the full round-out rather than the level pitch attitude I find common with some students.

During final the student should be encouraged to scan height, direction and speed. Achieved by scanning the aiming point, far end of the runway and of course the ASI. Once over the fence the ASI can be ignored. By scanning the aim point and the far end a better appreciation of height and direction is achieved. A student who scans only the aiming point will almost certainly round-out too high when confronted with a wide runway if he/she has trained solely on narrow strips! That student will also have difficulty with drift in crosswind landings.

DFC,

I agree. Accurate speed control will precede a good landing and 1.3 Vso (adjusted for gusts) is the only approach speed that works. Below fifty feet speed should be reduced to the stall. Ground effect will come into play and assist with the reduction in ROD. If not, power always works.

Tacpot,

As you suggest: Golden rule #1 never, ever, release back-pressure during the round-out!

Elsewhere in this forum is a thread on ‘point and power’ technique that deals with controlling airspeed with power and aim point with elevator. This technique works fine on the front side of the drag curve or the ‘area of positive command’. However once the aircraft is established at a speed below VminD or the back side of the drag curve the aircraft is in an ‘area of reverse command’ and airspeed should be controlled with elevator and ROD with power. Perhaps the ‘point and power’ technique is a factor in these accidents.

[Chuck Ellsworth]

Blue Hauler:

Hi, yeh there sure are some problems with how to judge landing height flare and hold off to acheive a proper touch down attitude.

Here is a point to ponder. I flew crop dusting for 7 years, we flared and held as low as one foot on some applications, the approach to the flare was about a forty five degree nose down angle in the drop in to the field, the aim point had to be the flare point, to look at the far end of the field would be useless to judge flare height and would result in flying right into the ground.

Also the easiest method to judge flare and touchdown is the constant turn to flare method, far easier to judge than a straight in approach.

Anyhow there is no way to win an argument with what method to use.

I have managed to get by without crashing into the earth using my method so it works for me. And by the way it works for all the pilots whom I teach advanced flying to.

You can bet when I finish with them they know how to flare and land either wheel landings or full stall.

It ain't rocket science, but there sure are a lot of pilots who must think it is rocket science cause they sure don't know how to do it properly, just look at the accident record.

bottom line...poor instruction = poor pilot.

Have fun.

Cat Driver:

...........
:D The hardest thing about flying is knowing when to say no.:D

[Blue Hauler]

Chuck


Nothing wrong with your method. I guess that is what we all achieve with experience. Ab-initio training does however require some ‘fly-by-the-numbers’ techniques until students attain the necessary experience to experiment and vary what works for them. When things go skew a reversion back to basics will always restore the equilibrium.

[Chuck Ellsworth]

Hi again Blue Hauler:

Where is YBBN?

It has become very common for instructors to teach their students to look at the far end of the runway to judge height for the round out / flare or whatever you wish to call the transition from the approach attitude to the level attitude that is necessary to arrest the rate of decent to prevent the thing from slamming into the earth at a high sink rate.

It matters not if it is a first time student or your Labrador retreiver that is attepmting to judge the flare height, simple triangulatin will prove that the further ahead you look the more shallow becomes the sight angle and the less accurate your ability to define the actual height above the surface.

The most accurate means to judge the closing rate with the surface and thus the actual height above same is to use the flare point as your reference during the latter stages of the approach. Once you determine the moment to begin the flare by reference to the flare point you then shift your sight point further ahead of that point.

Lets use another example of judging relative distance and sight angles to accomplish another task.

Imagine you are operating a Cat Bulldozer and your task is to make a level parking area in an uneven field that is one mile long and you are to make this level area at the south end of said field.

How sucessful do you think you would be in determining the proper angles for a level surface if you looked at the far end of the field one mile away, rather than looking at the target area where you were attempting to level the surface.

Judging landing height is no different, the further away one looks the less accurate your height judgement will be, same goes for your Lab. Retreiver he also will be less acurate in judging height the further away he looks.

There is a sad lacking of the understanding and teaching of attitudes and movements and proper attitude control in flight training to day. The ability to judge landing heights and attitudes are very basic and necessary skills to develope and also very easy to teach if the teacher understands the subject himself / herself.

Now please do not take this as any personal attack on you mate, that is not my intention, rather I am trying to develope an open and serious examination on why so many pilots stuff up on landing. :D :D

So you be nice to me, cause I am your friend. :)

Cat Driver:

[Centaurus]

DFC.
You make the point that if the aircraft hits and balloons the smart thing to do is to go-around and have another go.

And a thousand instructors have sent their students off on their first solo with the final advice of "when in doubt, go-around". It is a conveniently simple solution. Or is it?

Now I have a problem with this advice. A low energy go-around after a prolonged float or a big bounce with everything hanging out (40 degrees of flap in a C150, for example) has the potential to be quite a dicey manoeuvre unless expertly handled.

Invariably the aircraft is hanging up with nose high a few feet above the ground. Full power will cause an inevitable yaw which unless carefully checked, can lead to a serious excursion around the immediate horizon.

Unless the flaps are brought immediately to 20 degrees (C150) and the nose attitude lowered to a safe attitude, and a specific IAS of 55 knots aimed at - then a powered on stall and incipient spin can happen real fast.

All this from a mis-handled low IAS full flap go-around after the flare. This is no amateur manoeuvre - no matter how blithely an instructor can offer the advice "if uncertain then don't hesitate to take it around".

What seems to be lacking in ab-initio landing training is the technique of landing off the bounce by judicious use of nose attitude and power. It is generally a far safer option than a balls-to-the wall full flapped go-around by a nervous inexperienced pilot.

The bounced/ballooon/high flare recovery to land straight ahead is to my mind, an absolutely vital skill to be taught early in circuit training. Of course it all depends on how much spare runway you have left to play with. But is that any more critical than a low energy everything hanging out go-around with those trees/telegraph poles just off the end of the airstrip?

Too many instructors fail to ensure that their students are fully competent at low energy go-around in the flare - most are satisfied with a 1-200 feet agl go-around while the speed is nice and high. But the runway level low speed go-around is a different animal.

It is vital to equip your students with the skills to land off a porpoising bounce, balloon or a high flare. It can be a safer option than a high drag go-around with all the inherent dangers of an uncontrolled torque/slipstream yaw at critically low speed.

So think carefully when you advise your student to "when in doubt, just go-around". The "land on " option may be safer.

[Chuck Ellsworth]

Centaurus:

Amen, Amen ,Amen:::

Cat Driver