Sad Pic of Trident G-ARPY

[Garry Russell]

Aftermath of it's crash.

http://www.baaa-acro.com/1966/archives/ ... -4-killed/

[DogTailRed2]

Did the Trident have a problem with stalling flat?
This one looks to have bellied in and also the Staines disaster was a similar `flat` fate.

[Garry Russell]

It was it's first flight and engaged in stalling tests. The deep stall is a problem with all T tail designs. The Staines was caused by premature retraction of the droopers, causing the wings to stall. This was caused by tailplane stall. If the angle of attack gets too high the wing causes the tailplane to get into the wing shadow meaning the wing is stopping sufficient airflow over the tailplane. Lack of airflow means the elevators are in effective, the nose stays high and the speed reduces to virtually zero as can be seen by the wreckage. There are safety devices like stick shakers and stick pushers to get the nose down, but if disabled for testing purposes and a mistake is made this is the result. The One-Eleven prototype was lost in a deep stall and that was totally destroyed in the post crash fire. Had it not been for the fire the wreckage would probably looked very much like this.

[cstorey]

I have to say that the resemblance between G-ARPY and G-ARPI at Staines was chilling, and of course what was common to both these tragedies was that the stall protection equipment was disabled deliberately . In the case of BEA 548 had someone not done that ( and the Public Inquiry could not determine who did it ) they might still have got away with it

[Dev One]

It was it's first flight and engaged in stalling tests. The deep stall is a problem with all T tail designs. The Staines was caused by premature retraction of the droopers, causing the wings to stall. This was caused by tailplane stall. If the angle of attack gets too high the wing causes the tailplane to get into the wing shadow meaning the wing is stopping sufficient airflow over the tailplane. Lack of airflow means the elevators are in effective, the nose stays high and the speed reduces to virtually zero as can be seen by the wreckage. There are safety devices like stick shakers and stick pushers to get the nose down, but if disabled for testing purposes and a mistake is made this is the result. The One-Eleven prototype was lost in a deep stall and that was totally destroyed in the post crash fire. Had it not been for the fire the wreckage would probably looked very much like this.

I think that there was also a difference between the Trident & the 1-11 in that the 1-11 prototype had servo (i.e. aerodynamic servo) operated elevators, whereas the Trident had hydraulic operated controls, this meant that there was no way any amount of pushing & pulling on the control column would get it out of the deep stall. The 1-11 crash I believe was also the first recognition of deep stall, although it is believed that DH also had experienced it but not publicised the fact! DH & Vickers got together very quickly after the 1-11 crash to swap notes & subsequent 1-11's had a change to the elevator authority - hydraulic power ?
Am I talking rubbish ? again?
Keith

[Garry Russell]

Yes. The One-Eleven elevator control was very bad initially and that was a contributory factor. Many tests ending with the pilot complaining about elevator lag and loss of positive control as the speed dropped of for the flare. That was possibly the main cause of the heavy landing of G-ASJB. Increased elevator power, stronger springs, reprofiled wing LE and the changing of size and position of the wing fences were necessary. A stick shaker and pusher were fitted as was an angle of attack indicator, the two little tubes sticking out behind the forward door.