ATSB Report Kingair fatal at Wondai 26 July 1990
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ATSB Report Kingair fatal at Wondai 26 July 1990
https://www.atsb.gov.au/media/5226668/199003089.pdf
A newspaper report last week covered an interview with the relatives of the deceased of a Kingair crash at Wondai Queensland in 1990. It was the 30th anniversary of the crash. Wondering what happened I pulled up the ATSB report. See above link.
In short, it was a dark night takeoff. The aircraft was airborne for only a few seconds and flew into the ground wings level and exploded. It was a private flight.
The report suspected the pilot may have been a victim of somatogrovic illusion. While that may never be known, the following extract from the report is worth study if only because it comes up with interesting figures in terms of acceleration rates versus pitch-up angles.
Quote:1.17.4 The somatogrovic illusion
Under acceleration, the combination of gravity and the inertial forces produce a resultant force at an angle aft of the true vertical. Acting upon the human vestibular system, and in particular the semi-circular canals of the human inner ear, such forces can, in conditions of reduced or no visibility, give a pilot a false pitch up sensation.
That is, while the aircraft and pilot may be flying straight and level or climbing slightly, the pilot may have the sensation of climbing at a much steeper angle than they in fact are. Without some visual input to override this false sensation, the pilot will usually react to it as a real and accurate perception of his/her position and travel in space. The normal response to this situation is for the pilot to gradually push the nose of the aircraft down, resulting in the aircraft descending. This phenomenon is known as the somatogravic illusion.
The somatogravic illusion has been linked with a large number of accidents in which aircraft impacted unlit terrain under control shortly after take-off on dark nights. Although the illusion is generally associated with high performance military aircraft, it can arise in lower performance aircraft. For example, an aircraft accelerating from 100 to 130 knots in 10 seconds generates an acceleration on the pilot of 0.16 G, which is sufficient to produce the sensation of a 9 degree pitch-up.
Accident studies indicate that long pilot experience is no certain protection against "dark night take-off accidents". Pilots with limited recent night or instrument flying experience appear more susceptible to spatial disorientation, possibly because they may not be fully accustomed to (misleading) acceleration sensations. The level of recency may also affect instrument scan technique.
Calculations showed that VH-LFH accelerated at an average rate of 8.79 feet/second/second (0.275 Gs) from lift-off to impact. This would have been sufficient to produce the sensation to the pilot of a pitch-up of about 15.3 degrees.
Unquote. (My bolding in red)
Kingair pilots might find this useful info as well as flying instructors teaching night VFR. 15 degrees pitch up happens to be an average climb attitude for jet transports after lift-off. I had no idea that a somatogrovic illusion could be that severe.
A newspaper report last week covered an interview with the relatives of the deceased of a Kingair crash at Wondai Queensland in 1990. It was the 30th anniversary of the crash. Wondering what happened I pulled up the ATSB report. See above link.
In short, it was a dark night takeoff. The aircraft was airborne for only a few seconds and flew into the ground wings level and exploded. It was a private flight.
The report suspected the pilot may have been a victim of somatogrovic illusion. While that may never be known, the following extract from the report is worth study if only because it comes up with interesting figures in terms of acceleration rates versus pitch-up angles.
Quote:1.17.4 The somatogrovic illusion
Under acceleration, the combination of gravity and the inertial forces produce a resultant force at an angle aft of the true vertical. Acting upon the human vestibular system, and in particular the semi-circular canals of the human inner ear, such forces can, in conditions of reduced or no visibility, give a pilot a false pitch up sensation.
That is, while the aircraft and pilot may be flying straight and level or climbing slightly, the pilot may have the sensation of climbing at a much steeper angle than they in fact are. Without some visual input to override this false sensation, the pilot will usually react to it as a real and accurate perception of his/her position and travel in space. The normal response to this situation is for the pilot to gradually push the nose of the aircraft down, resulting in the aircraft descending. This phenomenon is known as the somatogravic illusion.
The somatogravic illusion has been linked with a large number of accidents in which aircraft impacted unlit terrain under control shortly after take-off on dark nights. Although the illusion is generally associated with high performance military aircraft, it can arise in lower performance aircraft. For example, an aircraft accelerating from 100 to 130 knots in 10 seconds generates an acceleration on the pilot of 0.16 G, which is sufficient to produce the sensation of a 9 degree pitch-up.
Accident studies indicate that long pilot experience is no certain protection against "dark night take-off accidents". Pilots with limited recent night or instrument flying experience appear more susceptible to spatial disorientation, possibly because they may not be fully accustomed to (misleading) acceleration sensations. The level of recency may also affect instrument scan technique.
Calculations showed that VH-LFH accelerated at an average rate of 8.79 feet/second/second (0.275 Gs) from lift-off to impact. This would have been sufficient to produce the sensation to the pilot of a pitch-up of about 15.3 degrees.
Unquote. (My bolding in red)
Kingair pilots might find this useful info as well as flying instructors teaching night VFR. 15 degrees pitch up happens to be an average climb attitude for jet transports after lift-off. I had no idea that a somatogrovic illusion could be that severe.
Pilots with limited recent night or instrument flying experience appear more susceptible to spatial disorientation, possibly because they may not be fully accustomed to (misleading) acceleration sensations. The level of recency may also affect instrument scan technique.
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Nasty business -(
Probably most of us have experienced some sort of disorientation during our careers, I know I have.
I'd hate to imagine just how many potential accidents like this where avoided just at the last second!
Probably most of us have experienced some sort of disorientation during our careers, I know I have.
I'd hate to imagine just how many potential accidents like this where avoided just at the last second!
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In accidents of this nature (dark night takoff) where the direct cause is unknown, ATSB usually mention the possibility of somosogravic illusion. It becomes a catch-all phrase. In this accident the pilot for some reason made an airborne report inside 20 seconds after lift off. That is poor airmanship and should have raised an ATSB eyebrow.
A black night takeoff on instruments demands the highest of instrument flying skills and sheer concentration. Talking on the radio at 100 feet off the ground was not a smart move. It would only take a few seconds after lift-off to relax one's grip on the control wheel and be slightly out of trim, to have a miniscule change of AH attitude either up or down. Old suction driven artificial horizons of that era had acceleration errors on takeoff causing erroneous attitude indications. Enough to be deadly at 100 ft AGL.in daylight, let alone at night.
The ATSB report mentioned VH-LKH was equipped with a Bendix M4D autopilot and flight director system. One avionics repair shop commented: "These and all attitude-based units from Bendix/King can be prone to gyro-induced flaws. Some possible symptoms of a gyro problem include shallow wing rocking and gentle pitch porpoising. The KI256 flight director gyro could be the problem."
In some ATSB reports we see reference to the pilots last instrument rating test and that nothing untoward was noticed by the Examiner. Well, a cynical view could be for obvious reasons of responsibility he would say that, wouldn't he?
One could speculate forever on this and similar night accidents where there was no obvious cause. The possibility of poor instrument flying ability at the time of the accident should not be ignored iin accidents of this nature.
A black night takeoff on instruments demands the highest of instrument flying skills and sheer concentration. Talking on the radio at 100 feet off the ground was not a smart move. It would only take a few seconds after lift-off to relax one's grip on the control wheel and be slightly out of trim, to have a miniscule change of AH attitude either up or down. Old suction driven artificial horizons of that era had acceleration errors on takeoff causing erroneous attitude indications. Enough to be deadly at 100 ft AGL.in daylight, let alone at night.
The ATSB report mentioned VH-LKH was equipped with a Bendix M4D autopilot and flight director system. One avionics repair shop commented: "These and all attitude-based units from Bendix/King can be prone to gyro-induced flaws. Some possible symptoms of a gyro problem include shallow wing rocking and gentle pitch porpoising. The KI256 flight director gyro could be the problem."
In some ATSB reports we see reference to the pilots last instrument rating test and that nothing untoward was noticed by the Examiner. Well, a cynical view could be for obvious reasons of responsibility he would say that, wouldn't he?
One could speculate forever on this and similar night accidents where there was no obvious cause. The possibility of poor instrument flying ability at the time of the accident should not be ignored iin accidents of this nature.
Last edited by sheppey; 28th Jul 2020 at 05:53.
In this accident the pilot for some reason made a departure report inside 20 seconds after lift off
Although 30 years ago, the same issues (illusions) keep reoccurring - the recent B767 accident discussion in the USA states that the pilot flying may have suffered the same illusion after inadvertently pressing the TOGA button. It proves that the statement "there are no new accidents" is indeed true...
Regarding the earlier comment that Flight Examiners don't seem to see these issues during IPC's, you need to bear in mind that IPC's (in light aircraft) are completed in daylight 99% of the time & that a true dark night takeoff & the potential illusions associated with that, are not assessed...
Regarding the earlier comment that Flight Examiners don't seem to see these issues during IPC's, you need to bear in mind that IPC's (in light aircraft) are completed in daylight 99% of the time & that a true dark night takeoff & the potential illusions associated with that, are not assessed...
Old suction driven artificial horizons of that era
I recall a few 2am departures from King Island in Twin Bonanzas in the early 1970's as a low instrument hour pilot. I was under no "illusions' about the importance of sticking to the AH like glue once the last runway lights disappeared under the nose. The occasional flash from the Cape Wickham lighthouse in my peripheral vision made it feel that the aircraft was banking. I can't imagine anything blacker than heading out over Bass Strait on an overcast night.
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Whilst the AH is our primary inst we mustn't forget the VSI, I believe one of the most important of the six pack.
As long as your speed is in the ball park & your wings are close enuf to level give me the VSI any day to know what's happening under my ass!
As long as your speed is in the ball park & your wings are close enuf to level give me the VSI any day to know what's happening under my ass!
Whilst the AH is our primary inst we mustn't forget the VSI, I believe one of the most important of the six pack.
Agree. The basic six pack of flight instruments was easy to assimulate especially as the artificial horizon was relatively large and the "little aeroplane" was quite big. Current EFIS has an AH that looks nothing like an aeroplane and the triangular image is shaped so the inverted V of a flight director can fit snugly when commands are satisfied. Add to that a tiny IVSI needle which belies its importance and the plethora of information that borders the whole display, can be quite overwhelming.
One US airline asked Boeing to design a basic six pack EFIS display with round dials without all the goodies surrounding it in the belief it helped the pilot maintain scan currency. Blind reliance on flight director commands has been the cause of many crashes over the years. In the case of the Kingair Wandai accident it was not known if the pilot was following FD commands or even if the FD was switched on and in view.
There is evidence that some pilots become addicted to following the flight director to the extent they even leave it in view when not being used. This can be distracting but addicted pilots accept that. The Boeing 737 FCTM states that if the flight director commands are not to be followed, the flight director should be switched off. That is sound advice for most aircraft.
