When a low level barrel roll goes wrong...

[TheGreenGoblin]

Both the Bolivan instructor and student were killed in March this year.



Sad to see...

[Boac]

Say no more!

[TheGreenGoblin]

As my flying instructor friend said to me when he saw the video...

I bet £100000 the instructor said,

“Watch this.”

[TheGreenGoblin]

I guess it was more of a failed victory/aileron roll than a barrel roll. Talk about snatching defeat from the jaws of victory...

The cue to the coming disaster was the sound of the aircraft throttling up above the runway.

[Boac]

Reminds me of the 74Sqn 'ace' who walked out to his Lightning saying to his friends and ground crew "Watch this for a reheat rotation take-off"

They did and he died.

[Pontius Navigator]

As a novice, what did he do wrong, it looked like he stopped the roll for some reason. No funny answers please.

[TheGreenGoblin]

I suspect he didn't trade altitude for enough speed. He had reduced power on the approach, you can hear him powering up as they did the flyby. I suspect it was a spur of the moment whim without enough kinetic energy to complete the manoeuvre. Ran out of speed in the climb/roll and the aircraft fell out of the roll partially stalled and entered a spin just prior to hitting the ground.

A different cause, in a twin, due to carburetor fuel starvation in a negative G situation, with the concomitant complication of asymmetric power, subsequent loss of kinetic energy, at Duxford, with equally fatal results...

[tango15]

I think this was taken at Barton Air Show. The pf was a former colleague, Kevin Moorhouse, who was a test pilot at Woodford. He started there as an apprentice and worked his way up. He had flown the Mossie many times and I have always been curious as to why he would make an error like that. The second man in the cockpit was Steve Watson, who maintained the aircraft at Hawarden, where it was based.

[Boac]

it looked like he stopped the roll for some reason

Unless there was some sort of control restriction I suspect he just ran out of aileron control as the speed reduced. I think only a boot of rudder would have saved the day, but who knows!

[TheGreenGoblin]

I think this was taken at Barton Air Show. The pf was a former colleague, Kevin Moorhouse, who was a test pilot at Woodford. He started there as an apprentice and worked his way up. He had flown the Mossie many times and I have always been curious as to why he would make an error like that. The second man in the cockpit was Steve Watson, who maintained the aircraft at Hawarden, where it was based.

You are quite correct, it was Barton. Your friend didn't make an error, it seems that a known issue with the Merlin engine\carburettor occurred at probably the worst moment it could have occurred. It is possible the pilot would not have known about this and not mentally prepared for a recovery in such a circumstance.

It was apparent that there was an perception among pilots who had flown the Mosquito, that Merlin engines were likely to suffer a momentary cut under reduced or negative g conditions, with the result that such events, when experienced, were not entered in the technical log...

The Merlin's reputation for cutting under negative g conditions had endured since the beginning of the Second World War. Curiously,the fact that a successful carburettor modification had been developed(and incorporated on the subject aircraft) to remedy the problem had largely been forgotten.

https://assets.publishing.service.gov.u ... 501355.pdf

[CharlieOneSix]

.....Curiously,the fact that a successful carburettor modification had been developed(and incorporated on the subject aircraft) to remedy the problem had largely been forgotten.

The famous Miss Shilling's orifice....
https://en.wikipedia.org/wiki/Miss_Shilling%27s_orifice

[TheGreenGoblin]

.....Curiously,the fact that a successful carburettor modification had been developed(and incorporated on the subject aircraft) to remedy the problem had largely been forgotten.

The famous Miss Shilling's orifice....
https://en.wikipedia.org/wiki/Miss_Shilling%27s_orifice

So for the want of a Shilling, the aircraft was lost.

Kudos to Ms Shilling, to have been a lady engineer at the time, midst all the bawdy men in the RAF, must have taken some sang froid on her part (oops another Freudian slip).

[Boac]

Do we know if the P Notes (Mosquito) advised against reduced or negative 'g' and did the pilot apply such during the manoeuvre? I have not seen any accident report.

[TheGreenGoblin]

Do we know if the P Notes (Mosquito) advised against reduced or negative 'g' and did the pilot apply such during the manoeuvre? I have not seen any accident report.

https://assets.publishing.service.gov.u ... 501355.pdf

[Boac]

Rather inconclusive.

[Pontius Navigator]

But if the modification had been incorporated was the known still relevant in this instance?

[TheGreenGoblin]

But if the modification had been incorporated was the known still relevant in this instance?

I guess that if the modification had been installed, the port engine wouldn't have rich cut, and the aileron roll would have proceeded smoothly and safely.

[Pontius Navigator]

TGG, but the earlier statement said it had been, serial 10 refers.

[TheGreenGoblin]

TGG, but the earlier statement said it had been, serial 10 refers.

I stand corrected. You are quite correct, it appears that the "fix" had been applied... but despite this, the carburetors were sub-optimal under negative G conditions, given the the relevant settings and tolerances..

The investigation of the carburettors revealed that neither unit met the specified fuel flow
requirements under negative g conditions,as the adjustable stops that controlled the float height
(which in turn controlled the float valve) were not even contacting the valve links. As noted earlier,
these stops should have been set at overhaul, and not touched by the operator. As a result, it was
found that the fuel flows for the one float valve of each carburettor that was capable of being tested
were reduced to approximately 10% and 50% of the required values for the left and right
units respectively. Assuming both float valves of each carburettor were in similar states, it is
probable that with either or both flats in their fully depressed positions, the reduced fuel flow would
not sustain the left engine at moderate power settings. It is rather more difficult however, to relate
the as-found condition of the carburettors to the likely effects on the engines during the wingover
manoeuvre that preceded the accident. The display sequence was similar to countless others,
although the display line was perhaps shorter than most, with an attendant possibility of steeper
manoeuvres at either end.

With the benefit of hindsight it is appreciated that gasket thickness can have a critical effect on the
dimensional relationship between the float valve pintle and the associated valve orifice.
Accordingly it would be advisable to recheck the restricted flow rate through the carburettor
following disturbance or replacement of the gasket. No such requirement was contained within the
maintenance manuals which were examined.

[Boac]

I cannot undesrstand why the right bank increased so much following suppod left engine failure. It will, I think, remain an unexplained, tragic and costly accident.