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-   -   Tiger Moth incident at Brimpton (https://www.pprune.org/accidents-close-calls/579953-tiger-moth-incident-brimpton.html)

CHAIRMAN 19th Jun 2017 15:15

Jam, Aussie and NZ Tigers have fuel drains installed at the rear of the tank following an accident in NZ caused by water entering a tank overnight whilst parked in rain. Mandatory AD. Anyway it's maybe not a factor in this accident.
Re the accident pic: A good landing attitude apart from the low wing. I can't imagine getting in to that position on t/off. The go is to get the tail up early. If the field is soft/wet then maybe a bit tail low. You get a feel for it after a bit of practice. As has been said, if the aircraft is not accelerating then try something else or give it away.
To be honest I've never attempted a three point takeoff in a Tiger, but I know of other tail wheel aircraft that have come to grief attempting it, but not deliberately.
Maybe tail wheel aircraft can lift off in ground effect lower than the stall speed in a three point attitude, but that's never going to end well unless the aircraft is very over powered - not the case with the tiger.
Any Aerodynamic experts out there?

B737C525 19th Jun 2017 20:55

Colled, it's not possible to send you a PM because you are a new member here, so forgive me asking publically: Did the investigators speak to you to gather your eye witness account?

JammedStab 19th Jun 2017 22:45


Originally Posted by CHAIRMAN (Post 9806611)
To be honest I've never attempted a three point takeoff in a Tiger, but I know of other tail wheel aircraft that have come to grief attempting it, but not deliberately.

Maybe tail wheel aircraft can lift off in ground effect lower than the stall speed in a three point attitude, but that's never going to end well unless the aircraft is very over powered - not the case with the tiger.

A standard soft field takeoff for a tricycle gear aircraft is done in a manner to lift off at the slowest possible speed at which point the nose is lowered in order to accelerate in the ground effect. It really shouldn't be too much different for a taildragger and at lower density altitudes shouldn't normally be a problem.

The acceleration might be slower in the Tiger(and similar aircraft) with all the drag involved but if you were able to get airborne, under normal circumstances I would think you can remain airborne in the ground effect cushion.

Immediately lowering the angle of attack reduces drag and acceleration should be equal to or better than it was while on the ground with its associated drag items.

colled 21st Jun 2017 08:54


Originally Posted by B737C525 (Post 9806967)
Colled, it's not possible to send you a PM because you are a new member here, so forgive me asking publically: Did the investigators speak to you to gather your eye witness account?

No they didn't ask me and I was not actually aware of any investigators going around asking for witnesses but I assume they must have asked for some witnesses though, surely! Anybody on here get asked? The AAIB report seemed to be an account from the pilot's perspective and was a bit vague on what actually happened. It sounded like he suddenly and unexpectedly departed the runway, aborted the flight and rolled into the car enclosure. In reality all control was lost hundreds of metres before the crash event, and from what I saw the flight was not aborted, it was still under full power and in the air (not rolling along the ground) just before it hit. The photo in the report tells a story though, showing a right wing drop on a stall attempting to be corrected by max left deflection of the ailerons, but no left rudder and also appears to be a dose of up elevator in as well.

Piltdown Man 21st Jun 2017 13:37

From memory, the process of taking off (into wind) on a tail dragger is to set full power with the stick full aft and then, using into wing aileron, as the aicraft accelerates move the stick forwards to unstick the tail until the "picture" is achieved. Then hold the picture, let the aicraft climb off the ground. On more powerful aircraft (180 Cub) it just happened a bit quicker. The trim was irrelevant and over-ridden if it was in the wrong place. The important things were "picture", airspeed and wings level. Furthermore, a lower seat would entice you to fly with a lower attitude and a high sear might give a better view if the surroundings.

PM

JammedStab 22nd Jun 2017 00:15


Originally Posted by colled (Post 9808350)
The photo in the report tells a story though, showing a right wing drop on a stall attempting to be corrected by max left deflection of the ailerons, but no left rudder and also appears to be a dose of up elevator in as well.

One would think that if the aircraft had been rolling to the right, regardless of the reason, that the pilot would instinctively be applying opposite aileron input which may not be helpful in a stalled condition.

That being said, the DH.82 ailerons are a bit unique in that full aileron deflection is achieved not at full control stick deflection to the left or right but at perhaps 75 percent deflection after which the downgoing aileron returns almost to neutral although the upgoing aileron continues deflecting upward at an increasing ratio at the same time which is quite substantial(what were newly patented differential ailerons). That being said, in my experience, when doing a control check, I could only achieve about 75 percent stick deflection before the stick was blocked by my legs. All of which conveniently meant that max possible stick deflection gave max downward aileron deflection.

In the picture, I don't see up elevator and see prepaid some aileron input.

JammedStab 22nd Jun 2017 00:17


Originally Posted by Piltdown Man (Post 9808600)
From memory, the process of taking off (into wind) on a tail dragger is to set full power with the stick full aft and then, using into wing aileron, as the aicraft accelerates move the stick forwards to unstick the tail until the "picture" is achieved. Then hold the picture, let the aicraft climb off the ground.

The trim was irrelevant and overridden if it was in the wrong place

PM

What about the tail skid causing excess drag if full aft elevator is applied?

I have never taken off with the trim like this so it is not appropriate to comment unless one has or is aware of the result of doing so.

Piltdown Man 23rd Jun 2017 10:35

There is not that much drag. Full aft is applied only long enough to get the thing rolling. With the onset of elevator authority the stick is moved forwards to lift the tail. From memory, that only took a few seconds.

PM

biscuit74 23rd Jun 2017 20:45


Originally Posted by JammedStab (Post 9807052)
A standard soft field takeoff for a tricycle gear aircraft is done in a manner to lift off at the slowest possible speed at which point the nose is lowered in order to accelerate in the ground effect. It really shouldn't be too much different for a taildragger and at lower density altitudes shouldn't normally be a problem.

The acceleration might be slower in the Tiger(and similar aircraft) with all the drag involved but if you were able to get airborne, under normal circumstances I would think you can remain airborne in the ground effect cushion.

Immediately lowering the angle of attack reduces drag and acceleration should be equal to or better than it was while on the ground with its associated drag items.

I agree - that's the way I was taught soft or rough field take-offs in taildraggers and low power machines - once in the ground effect easing to hold level just off the ground allows acceleration.
Stick forward to get the tail off, then back stick to get airborne quickly at lowest feasible airspeed. In some low power beasts on rough ground I was taught to use full back stick until airborne, then push forward firmly to hold level in ground effect, then accelerate away. It did need vigorous control - and I'd always use trim forward of neutral.

JammedStab 25th Jun 2017 13:50


Originally Posted by Piltdown Man (Post 9808600)
From memory, the process of taking off (into wind) on a tail dragger is to set full power with the stick full aft and then, using into wing aileron, as the aicraft accelerates move the stick forwards to unstick the tail until the "picture" is achieved. Then hold the picture, let the aicraft climb off the ground. On more powerful aircraft (180 Cub) it just happened a bit quicker. The trim was irrelevant and over-ridden if it was in the wrong place. The important things were "picture", airspeed and wings level. Furthermore, a lower seat would entice you to fly with a lower attitude and a high sear might give a better view if the surroundings.

PM

Under normal circumstances, I personally taught people to keep the tail somewhat down during the takeoff roll when it came to soft field takeoffs in tailwheel aircraft including the Tiger Moth(tail off ground but not aircraft level). The reason being that it makes it less likely to nose over. If you hit a soft spot, depression, make an incorrect input, etc, you could be in trouble. I really don't like being close to level during the takeoff roll on non-paved surfaces. The more nose heavy the aircraft type, the less comfortable I am in that situation.

Take a look at this video. Is there really any reason to have the tail up so soon? Then look at what happens.

https://www.youtube.com/watch?v=RjFgu_RiGsg

Bottom line....in tailwheel aircraft, I much prefer to be in a nose up attitude for takeoff and landing on soft fields.

Piltdown Man 25th Jun 2017 15:06

Interesting video. A little too much forward stick methinks.

PM

JammedStab 25th Jun 2017 15:42


Originally Posted by Piltdown Man (Post 9812021)
Interesting video. A little too much forward stick methinks.

PM

I agree. You can see the nosedown elevator input unlike in the picture of the one that crashed. Makes a good comparison(keeping in mind that the Brimpton pic is a snapshot in time).

If your pitch attitude target is a bit tail low after raising the tail and you accidently overshoot, you are merely in a level attitude. If your target is a level attitude and you accidentally overshoot, your attitude may be similar to what is seen in the video.

Vilters 26th Jun 2017 19:09

An unfortunate but rather typical issue here.

It is less dangerous to have a LOW time pilot fly a Complicated aircraft, then it is for a ULTRA high time commercial pilot fly a SIMPLE Aircraft.

Many moons ago, I was offered a ride in a private jet, flown by "the" company pilot.

The FIRST time the guy touched the yoke was when it was time to rotate.
That told me all I needed to know about this particular pilot.
I booked an airline ticket to get home. Once was enough.

Personally, I would have NO problem to put a Piper Arrow certified pilot in a Mooney.
I'd never put a Mooney pilot in a Jodel without proper training.

Those "know and seen it all guys" are ready for accidents to happen.

currawong 27th Jun 2017 09:16

Would like to see the stats to back that statement up.


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