RAF Non-operational loss 21 March 1944

[Observer1940]

Originally Posted by Arjay1949

Just goes to show how difficult it is for us to be definitive on the facts!

We have JP137 down as a MKII Series 1, not a MK II Series 1A, and the second record card actually describing the fact that the rudders had not been modified to cure the stall problem. (copy attached)

Yet you say the JPXXX range were fitted with modified rudders, making them MK II series 1A aircraft ??

Back to the drawing board for us, I think!

Thanks for this new info!

On the Accident Card shown it is a Mk II and does not have the modified rudders. I also see the reference to a wing dropping and a "spin".

Generally, there was rudder overbalance and it is recorded that the first Halifax Rudder Modifications did not solve the problem according to the A & AEE in 1943:-

"When rudder locking takes place, the rudder overpowers the ailerons completely and the aircraft rolls over to the side in which the rudder is applied. At the same time, the nose drops, and the aircraft enters a spiral dive."

"If the Pilot pulls the control column back as the aircraft rolls over and drops its nose as he would instinctively do then the controls are set for a spin and, unless action is taken quickly ... a spin may result."

"In any case there is a large height loss of anything up to 4,000 feet during recovery."

If he had recently taken off, he would likely not have enough height to recover the aircraft. That is why the Inquiry is saying the modification is really required.

Generally with an engine problem more rudder is also applied to maintain track, so if an engine was on fire and the Pilot needs more rudder any problem with rudder overbalance / locking is likely to be compounded.

During 1943 tests, they tried limiting the rudder travel and also thicker cord on the rudder trailing edges, to make them feel heavier to the Pilot and hopefully prevent the rudder reaching the overbalance stage, but the thicker cord did not improve the rudder locking characteristic. The rudders were considered too heavy for general flying and the thicker cord made the rudders unpleasantly heavy according to the A & AEE.

They next tried some factory modified rudders which were tested and these also suffered from overbalance troubles.
Rudder limit stops were recommended and more training of Pilots in recovery techniques in No.4 Group.

However, the problem was only really settled with a new larger redesigned 'D' fin area (40% larger fin area) and rudder combination and when tested there was no tendency to overbalance in various flight conditions.

This aircraft did not have the modified rudders and I feel you can clear the Pilot of blame. Also sufficient height to attempt a recovery was likely insufficient and if an engine was also on fire, his problems were made worse.

Mark