When all else fails blame somatogravic illusion
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When all else fails blame somatogravic illusion
Shorts 360 crashes into sea after dark night departure.
https://www.skybrary.aero/index.php/...f965-276530305
An allied story from 60 years ago. And it could not have been what we now call Somatogravic Illusion. Lincoln bomber doing touch and go circuits at Townsville on Runway 01 (called 02 in those days). The Lincoln designed as single pilot operated. The pilot under check that night was a former wartime Bomber Command Lancaster pilot. He was a decorated pilot with the DFC.
Instructor (Centaurus) in RH seat RAAF QFI experienced on Lincolns. At 1000 feet after take off with no horizon and now over water, a right turn to approx. 045 degrees magnetic was required towards Cape Bowling Green and plan was to climb to 5000 feet and return for VHF/DF instrument approach.
Flap retract was commenced at 1000 feet with IAS about 125 knots. Planned climb speed 140 knots. Slight nose down change of trim occurs during flap retract. During flap retract, the instructor looking across the cockpit to the pilot's instrument panel, noticed the rate of climb which was approximately 700 FPM was gradually turning into a rate of descent of 200 FPM while turning. The pilot under test was flying manually and completely on instruments at the time. The instructor observed the radio altimeter also reducing and after waiting for the pilot to notice what was happening, and nothing was happening except the aircraft was steadily descending, the instructor told the pilot to watch the VSI which was showing down instead of up.
With an oath the pilot jerked back on the control column and resumed the climb. The direct cause of the incident was poor instrument flying scan during trim change at flap retraction. Several months later the same captain nearly flew back into the ground during flap retraction after a night take off from Darwin while turning to set course overhead the aerodrome.
With no instruments on his side of the cockpit, the co-pilot did not see what was happening. What saved the aircraft was a pilot passenger occupying the bomb aimer seat in the nose of the aircraft who felt the aircraft sink as the flaps came up and noticed through breaks in low scud the ground coming towards them. He shouted on the intercom for the pilot to pull up which he did. In both cases there was very little acceleration felt. In both cases the cause was simply poor instrument flying skill.
It is the writer's opinion that where an investigation is unable to prove a specific cause of a night departure accident, which may have simply been the result of poor instrument flying scan at the time, somatogravic illusion is sometimes used as a fall-back most probable cause.
https://www.skybrary.aero/index.php/...f965-276530305
An allied story from 60 years ago. And it could not have been what we now call Somatogravic Illusion. Lincoln bomber doing touch and go circuits at Townsville on Runway 01 (called 02 in those days). The Lincoln designed as single pilot operated. The pilot under check that night was a former wartime Bomber Command Lancaster pilot. He was a decorated pilot with the DFC.
Instructor (Centaurus) in RH seat RAAF QFI experienced on Lincolns. At 1000 feet after take off with no horizon and now over water, a right turn to approx. 045 degrees magnetic was required towards Cape Bowling Green and plan was to climb to 5000 feet and return for VHF/DF instrument approach.
Flap retract was commenced at 1000 feet with IAS about 125 knots. Planned climb speed 140 knots. Slight nose down change of trim occurs during flap retract. During flap retract, the instructor looking across the cockpit to the pilot's instrument panel, noticed the rate of climb which was approximately 700 FPM was gradually turning into a rate of descent of 200 FPM while turning. The pilot under test was flying manually and completely on instruments at the time. The instructor observed the radio altimeter also reducing and after waiting for the pilot to notice what was happening, and nothing was happening except the aircraft was steadily descending, the instructor told the pilot to watch the VSI which was showing down instead of up.
With an oath the pilot jerked back on the control column and resumed the climb. The direct cause of the incident was poor instrument flying scan during trim change at flap retraction. Several months later the same captain nearly flew back into the ground during flap retraction after a night take off from Darwin while turning to set course overhead the aerodrome.
With no instruments on his side of the cockpit, the co-pilot did not see what was happening. What saved the aircraft was a pilot passenger occupying the bomb aimer seat in the nose of the aircraft who felt the aircraft sink as the flaps came up and noticed through breaks in low scud the ground coming towards them. He shouted on the intercom for the pilot to pull up which he did. In both cases there was very little acceleration felt. In both cases the cause was simply poor instrument flying skill.
It is the writer's opinion that where an investigation is unable to prove a specific cause of a night departure accident, which may have simply been the result of poor instrument flying scan at the time, somatogravic illusion is sometimes used as a fall-back most probable cause.
Last edited by Centaurus; 3rd Apr 2018 at 13:10.
I haven’t flown either type, but the difference appears to be that in your case with the flap retraction there was a nose down pitch change, whereas with the shorts there was a longitudinal acceleration. As I’m sure you know the normal trigger for the SI is longitudinal acceleration that is perceived by the pilot as undue pitch up, which is corrected by deliberate nose down inputs, that exacerbate the acceleration. Etc etc
What was the airspeed doing in your Lincoln?
The classic accident pattern of a somatogravic illusion is the steadily increasing airspeed, something that you don’t mention as being a factor in the Lincoln incident, which from what you state sounds like poor scan. But the steadily increasing airspeed was present in the shorts accident.
What was the airspeed doing in your Lincoln?
The classic accident pattern of a somatogravic illusion is the steadily increasing airspeed, something that you don’t mention as being a factor in the Lincoln incident, which from what you state sounds like poor scan. But the steadily increasing airspeed was present in the shorts accident.
