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Old 14th Jan 2018, 02:33
  #398 (permalink)  
G0ULI
 
Join Date: Dec 2013
Location: Norfolk
Age: 62
Posts: 0
Concours77

You may wish to revisit your figures.

The acceleration of an object in free fall under Earth's gravity is 32 feet per second, per second, or approximately 9.81 metres per second per second. I will stick with imperial units here.

The wingspan of the Electra is 99 feet, putting the centre line of the aircraft 49 feet 6 inches from the wing tip.

The top of the embankment is recorded as being 25 feet above the surrounding land. The power lines would be raised above the embankment by some arbitary figure to prevent electrocultion risk to passers by.

If the aircraft wing hit the embankment at an angle of between 60 and 70 degrees, even hitting the base of the embankment would place the fuselage centre line a minimum of 30 feet above the top of the embankment. The propellor strike marks indicate that the wingtip struck the embankment significantly higher up, no more than half way. So no more than 12 feet of the wingtip was likely to have made contact. This places the centre line of the fuselage roughly 42 feet above the top embankment and therefore 77 feet above the surrounding lower ground.

The aircraft travelled 380 feet before making the first solid impact with the ground. Allowing for the descent to be in free fall, the time taken to hit the ground would be roughly 1-1/2 seconds.

380 feet travelled in 1-1/2 seconds equates to a speed of 173 mph, or around 160 knots. Exactly what we would expect to see in a take off and climb flight profile. These are the minimum speeds needed to achieve the observed results. The true speed could perhaps have been 20 mph (17 knots) higher. Any extra speed and/or air resistance opposing a free fall drop would allow for the known 5 to 10 nose downward flight path while still allowing 380 feet of flight beyond the embankment.

Naturally these figures are back of an envelope calculations, but close enough to agree with the known aircraft performance figures, the figures given in the report, and to substantiate claims that the aircraft could and did strike the ground with a wings vertical bank angle.

[I have assumed the width of the fuselage to be 10 feet to simplify my calculations.]

I don't just compose these posts without considering the maths involved. On the other hand I really can't be bothered working through all the trigonometry to give a range of figures to satisfy every possible answer to the nearest inch for every possible bank angle and velocity.

There can be absolutely no doubt that the aircraft crossed the embankment at an angle of 60 to 70 with the right wing tip making contact with the embankment. The main impact with the ground occured with the right wing aligned between 90 and 100 vertically aligned to the ground, exactly as the investigators of the time stated. What happened after that is conjecture and guesswork.

The laws of physics don't lie.

Last edited by G0ULI; 14th Jan 2018 at 04:13.
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