Torque Stalls

LOW AND SLOW – IS THE WAY TO GO – PERMANENTLY!

Sadly demonstrated by Barney Warbrick at Waiuku on 16th August 1944, whilst I was still flying Kittyhawks at Ohakea. Flying his Corsair low and slow with wheels and flaps down and canopy open to wave to his brother-in-law driving the local cream lorry, as he applied power to climb away his Corsair was seen to give a violent shake, then roll to the left into a vertical dive into the Waiuku golf course.

A perfect example of a “torque stall” – easily possible with a 2000 hp aircraft at a very low speed, but very unlikely at a higher speed.

To absorb its 2000 hp, before four-bladed propellers were developed,(F4U-4) its large 13 ft 4 inch three-bladed propeller would be sending a massive rotating air mass rearwards over the inner wing sections, thus increasing the angle of attack on the left wing, already near the stall angle, and the downwards flow onto the top of the inner right wing would reduce its angle of attack making it further from the stall angle.

Further aggravating the situation, the rotation of the propeller turning clockwise would cause the aircraft to roll to the left – further increasing the effective angle of attack of the left wing to beyond its stall angle – with the inevitable result of a steep dive into the ground!

Unfortunately, the Corsair with its 2000 hp engine, and large propeller, and 50° of flap provided the perfect scenario for a torque stall during a carrier approach, particularly if the pilot got a little too low, and applied high power to correct it!

Although not a carrier pilot, from my own extremely short-landing experience at Waiheke 1820 times, approaching a few degrees steeper, using the Corsairs full 50° flap setting, but requiring less power than the flatter approach, it would be less likely to reach the critical situation described below!  I imagine that with a 50° flap setting, and getting a little low on the final stages of an approach, at an absolutely minimal approach speed,  the excessive amount of power necessary to rectify the situation would created an almost suicidal situation – for the reasons described above!

From the Corsair handbook.

“The stall with power on is rather abrupt, particularly with flaps down, but is preceded by some warning in the nature of buffeting. In the carrier approach conditions, the approach to the stall is indicated to some extent by increasing left wing heaviness, and the increasing amount of right rudder required. The stall in this condition (flaps “DOWN”  and “POWER ON”) is accompanied by a roll to the left and a near vertical recovery dive.”

Barney Warbrick’s crash at Waiuku 16/8/1944

Sgt/Pilot Barney Warbrick was the first member of the Ngati-te-Ata tribe

to qualify as a pilot, and had trained on Tiger Moths at Taieri, Harvards at Calgary in Canada, and Kittyhawks at Ohakea. Out on a local flight from Ardmore, he recognised  his brother-in-law’s truck on the road near Waiuku, carrying a load of cream to the dairy factory. He was seen to fly “low and slow” over the truck and wave and wave out to his brother-in-law. With wheels and flaps down, he was heard to apply power to climb away. But his aircraft appeared to give a violent shake, then roll rapidly to the left, diving vertically into the ground near the centre of the Waiuku golf course.