NTSB report shows that loose screws led to trim tab loss on Leeward's P-51

[Widewing]

As the subject says...

530 mph at the time of the failure.... Way fast!

http://www.msnbc.msn.com/id/48801527/ns/us_news-life/

We discussed this on the BBS at the time:

http://bbs.hitechcreations.com/smf/index.php/topic,320374.30.html

http://bbs.hitechcreations.com/smf/index.php/topic,320672.0.html

[715]

Does the loss of a tiny trim tab make a plane uncontrollable?  (I'm not commenting, I'm asking a question I don't know the answer to.)

[Widewing]

Does the loss of a tiny trim tab make a plane uncontrollable?  (I'm not commenting, I'm asking a question I don't know the answer to.)

Briefly, yes. At the speeds these unlimited racers fly, they have to trim nose down to reduce the aero induced stick forces that want to cause the aircraft to climb. When the only elevator trim tab fails, literally falls off, the aircraft will pitch up violently. In this case, the pitch-up loaded the pilot and airframe to at least 9g. The 74 year-old pilot was quickly rendered unconscious. The much modified P-51 now uncontrolled, rolled and dove into the ground.

[Krusty]

Wow... sobering news. I always wondered what the final ruling was.

Thanks for the info, WW.

[MK-84]

Briefly, yes. At the speeds these unlimited racers fly, they have to trim nose down to reduce the aero induced stick forces that want to cause the aircraft to climb. When the only elevator trim tab fails, literally falls off, the aircraft will pitch up violently. In this case, the pitch-up loaded the pilot and airframe to at least 9g. The 74 year-old pilot was quickly rendered unconscious. The much modified P-51 now uncontrolled, rolled and dove into the ground.

A trim tab can cause that much force?  Why is the plane not adjusted to fly at those speeds with no trim (doesnt that create a ton of drag)?  and use manual adjustments for takeoff and landing?

I'm talking about a purpose built racer, and I assume that the reason the plane works the way it does is because someone knows alot more than me.  Can anyone add to this?

[icepac]

The plane going 500mph will eventually have to land.

To land, it will have to be flyable at a low speed.

The hardware required to fit a variable incidence horizontal stabilizer would enlarge the fuselage in that area to an unaccaptable as well as adding mass to the rear of the plane.

[Wmaker]

A trim tab can cause that much force?  Why is the plane not adjusted to fly at those speeds with no trim (doesnt that create a ton of drag)?  and use manual adjustments for takeoff and landing?

I'm talking about a purpose built racer, and I assume that the reason the plane works the way it does is because someone knows alot more than me.  Can anyone add to this?

[Charge]

"The hardware required to fit a variable incidence horizontal stabilizer would enlarge the fuselage in that area to an unaccaptable as well as adding mass to the rear of the plane."

I don't think so. It is really just a designer's choice to make it controllable or not and you can ask why not. Complexity, price, ease of service are all affecting the final choice. I'd say that the weight difference would be negligible.

In fact the P-51 would be faster with trimmable tail plane as you would not need to trim the elevators downwards to keep the plane flying straight and thus it would induce less drag.

-C+

[GScholz]

If they could fit it in the 109 they can fit it in anything.

[MiloMorai]

If they could fit it in the 109 they can fit it in anything.

And the Fw190.

[icepac]

"The hardware required to fit a variable incidence horizontal stabilizer would enlarge the fuselage in that area to an unaccaptable as well as adding mass to the rear of the plane."

I don't think so. It is really just a designer's choice to make it controllable or not and you can ask why not. Complexity, price, ease of service are all affecting the final choice. I'd say that the weight difference would be negligible.

In fact the P-51 would be faster with trimmable tail plane as you would not need to trim the elevators downwards to keep the plane flying straight and thus it would induce less drag.

-C+

You can pose this pondering at the AAFO forums where the guys who build and race these planes communicate.

http://www.aafo.com/hangartalk/forumdisplay.php?f=2

[Krusty]

Ju87, Me262, and a bunch of others had full surface trim, also.

It's just part of the design. It's probably very hard and very involved to take a plane that doesn't have this, and build it INTO the plane. It's not a simple swapping of parts. It's major redesign of the structure and the supports and the connection points.

Racers will most likely keep the trim controls they were built with.