Snap Roll!
By: —Chuck Miller, Lt. Col. USAF (Ret)
av8or@eos.net
During my duties at O’Hare IAP with ConAC in the early 60s,
I was a Functional Check Flight (FCF) Pilot with responsibilities to perform test flights
on the unit aircraft after major maintenance work had been accomplished.
On one FCF I was pilot in command after an aileron change had been accomplished.
Our flight was to verify the rigging by doing inflight approaches to stall, both
“clean” (gear and flaps retracted) and “dirty” (gear down, flaps full down).
Our actual stall speed observations on the test flight would then be compared to those
predicted by the flight manual for our gross weight to verify that the airplane performed
within flight manual parameters, thus verifying there was no major rigging discrepancy.
The initial approach to stall was entered at 5000’ in a clean configuration,
making a gradual transition from wings-level cruise into slow flight and then into the stall buffet.
I experienced a normal and distinct stall buffet a couple of knots above flight manual predicted
values and the recovery was made by easing back pressure and adding power.
At that point, without much thought, and still at a relatively slow recovery airspeed (~ 60 knots),
I called for gear down and full flaps while still holding about 65% power.
With all the drag out and less than about 15 knots to lose to the stall,
I ended up with the throttles still partially open and rapidly decaying airspeed
as I continued to apply back pressure waiting for the stall buffet.
The buffet from the extended flaps and gear (as compared to the previous clean configuration)
very effectively masked the approaching stall buffet, and I suddenly found the aircraft
in a near-inverted 110 to 120 degree roll to the right.
I saw my startled co-pilot’s hands dangling over his head and
our lap charts were headed for the ceiling of the cockpit!
As any experienced multi-engine prop jock knows, doing power-on stalls
is a sure fire way for the prop wash to flip the aircraft on its back.
(I later learned that many twin-engined C-123 “Ranch Hand”
aircraft were lost in Vietnam in this very way when they were
flying tree-top missions and lost an engine
due to enemy ground fire or bird ingestion).
Of course the recovery was almost instinctive — throttles to idle and ailerons to the left
while holding neutral elevator forces.
This was definitely NOT in the training syllabus,
but the lesson learned here probably
saved my life several years later while flying in Vietnam!
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