Stalling & Force Landing

[Genghis the Engineer]

To the best of my knowledge, commercial pilots don't write reports, they fly aeroplanes.

Instructors, examiners, journalists and test pilots write reports. If you want one, here's an extract from one of mine, flying a STOL 2-seater as a Test Pilot.


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Stalling, config L, idle, 1kn/s

QTY 4 idle, wings-level, 1 kn/s stalls were carried out at a height of 3,000 to 3,500 QNH with the aircraft trimmed to 40 mph IAS and full (40°) flaps selected (defined as config L). The stall was defined by a firm pitch break (which occurred before full back-stick was obtained), and the recovery used was full power and centralisation of the control column. The following tabulated results were obtained, all speeds are mph IAS:-


[Pprunevision can’t cope with tables, so deleted]


The wings level idle stall in the landing configuration was benign, well defined, with some warning being furnished by airframe buffet 7-12 mph IAS (3-5 kn CAS) before the stall. Wing drop was minimal. This is considered satisfactory and compliant with BCAR S201. With prompt recovery using the Instructors handbook, the height loss is under 50 ft.

At aft CG, VSO is 20-25 mph IAS, which equates to 31.5 to 33.5 kn CAS.

Because aft CG will give the lowest stalling speed, landing configuration stalls at MTOW should be repeated near to the Fwd CG limit to confirm that Vso remains at or below 35 kn CAS.

It was considered, based upon this result, that Vso is likely to be about 35 kn CAS at fwd CG. This means that for compliance with BCAR S335(b), VF must be at-least 70 kn CAS. At present it is 52 kn CAS. Means of increasing VF to at-least 70 kn CAS (87 mph IAS on this aircraft) must be explored to ensure compliance with S335(b).

Stalling, PLF, wings-level, config L
QTY 3 stalls were flown in config L with power for level flight (nominally 2,500 rpm) set at 3,000-3,500 ft QNH and the aircraft initially trimmed to 42 mph IAS. In each case, stall warning was furnished by barely perceptible airframe buffet at 25 mph IAS (33 kn CAS) but far more significantly a 40-45° nose-up pitch attitude, which latter gave very clear stall warning. The stall occurred in each case at an indicated air speed of 10 mph IAS (on the low speed ASI needle stop, but estimated from extrapolation of previous test results to be 25-30 kn CAS). The stall was marked by a nose-down pitching motion to 30° below the horizon and 30°/40°/45° right wing drop. Recovery was instantaneous upon moving the stick forward and correcting the bank angle immediately afterwards using the ailerons. Height loss in recovery was nil, power not having been reduced.

Whilst stalling in PLF was exciting, there was adequate stall warning and recovery could be effected immediately, without height loss. Stalling in config L / PLF was considered satisfactory, although the POH should warn that a very high nose-up attitude is the best warning of the stall.



Summary of Conclusions

The wings level idle stall in the landing configuration was benign, well defined, with some warning being furnished by airframe buffet 3-5 kn CAS before the stall. Wing drop was minimal. This is considered satisfactory and compliant with BCAR S201.

Idle, turning flight stalls, at 30° of bank in the landing configuration were satisfactory and compliant with BCAR S201.


Summary of Recommendations

Aircraft

None.

Operators Manual

The operators manual should advise that the wings level idle stall in the landing configuration is benign, with some airframe buffet 3-5 kn before the stall, and little or no wing drop.

With prompt recovery using the Instructors handbook, the height loss is under 50 ft from an idle power stall, in level flight and 100ft with up to 30° of bank.

The operators manual should advise that with cruise or climb power selected, a very high nose-up attitude (exceeding 35° nose-up) is the best indication of an impending stall. If the aircraft is pushed to the point of stall approximately 60° wing drop accompanied by a strong nose-down pitching motion can be expected, likely to require about 200 ft to recover from.

Operators should be warned that although low-speed, tight turns are unlikely to cause a loss of control, they can potentially lead to an engine stoppage.


Further Testing

Landing configuration stalls at MTOW should be repeated near to the Fwd CG limit to confirm that Vso remains at or below 35 kn CAS.


Analysis

Means of increasing VF to at-least 70 kn CAS (87 mph IAS on this aircraft) must be explored to ensure compliance with S335(b).