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Old 1st Jan 2018, 18:36
  #86 (permalink)  
sky9

Keeping Danny in Sandwiches
 
Join Date: May 1999
Location: UK
Age: 72
Posts: 1,281
From the Transport Canada report identified by The Wala Zone:


In 1947, the Beaver was certified to British Civil Airworthiness Requirements and its stall characteristics were found to be acceptable. However, the Beaver demonstrates little or no pre-stall buffet and, if a warning system is not installed, the onset of the stall may surprise pilots.

Test flights conducted in 1992 showed that the float-equipped Beaver (aft CG limit, wings level and at maximum continuous power) stalled at 55 mph indicated airspeed (IAS) with flaps in the takeoff setting and at 54 mph IAS with flaps in the landing setting.

Turn stall tests were not performed with a float-equipped Beaver. When a wheel-equipped aircraft was stalled at a 30 bank angle, it pitched nose down and rolled both into and out of the turn. The maximum roll was 50. The maximum altitude loss was 100 feet before a pilot, using the proper technique, regained controlled flight. The test pilot noted that the Beaver displayed little or no pre-stall warning buffet.

Certification flight tests are conducted under controlled conditions. Under less than ideal conditions, like wind turbulence and unintended sideslip, stall characteristics could be aggravated with larger roll angles and increased altitude loss. Additionally, when an aircraft is unintentionally stalled, a pilot may not immediately recognize the condition and altitude losses in excess of 100 feet could be expected.

Some of the effects of an aft CG include:

decreased stall speed of an aircraft;
decreased longitudinal stability;
violent stall characteristics; and
poor stall recovery. 12
A 2009 FAA memorandum described the stall characteristics of the Beaver with a forward CG as being docile and predictable. However, many approved modifications have been applied to increase payload and make it easier to load to the aft CG limits. The FAA suggests the Beaver's stall characteristics in an aft CG condition are unstable and unpredictable, and that flight excursions with an aft CG are often unrecoverable at low altitude.
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