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Field In Sight
10th Feb 2004, 17:33
Hi,

During my hour building days, a friend and I had lots of fun making a C150 act like a mini Vomit Comet.

i.e. we would put the nose down to about 130 kts, pull up to 45 degrees and then use enough forward pressure to make things float around the cockpit "Apollo 13 The Movie" style.

Because we had zero G conditions in the aircraft, I assumed that both the occupents (us) and the aircraft were experiencing a downwards acceleration of 1g and therefore the aircraft had a load factor of zero. i.e. it was free falling.

I think I have understood correctly but would welcome any comments to the contrary, particularly because of the -1g limit.

Thanks,

FIS.

OzExpat
10th Feb 2004, 19:20
Because we had zero G conditions in the aircraft, I assumed that both the occupents (us) and the aircraft were experiencing a downwards acceleration of 1g and therefore the aircraft had a load factor of zero. i.e. it was free falling.
What? By your own statement, things were floating around the cabin, so I don't think your statement is correct. I was actually going to use the word "hogwash", but I figured that would be a bit too emotive for this forum.

Are you trying to clear your conscience?

In absense of a gauge, you will never know exactly how much negative "g" you were pulling at the time. I suspect that the aeroplane could've been overstressed by that manoeuvre so, it's probably an accident looking for somewhere to happen. Or has the accident already happened?

I hope not.

SquawkModeA
10th Feb 2004, 19:38
It's true that you never really can tell the exact load factor without a gauge; however with things floating around in the cabin it would have been more or less free falling with around 0-g conditions.

Consider that with a load factor of -1 g things would have been pulled towards the roof with the same force they are normally pulled towards the floor with.

Kerosene Kraut
10th Feb 2004, 19:59
Hope your friend made sure the a/c was fit for that type of maneuvring. Had a chap at flight school who did the same with our secretary (at night and over the montains...) in one of our standard 152/172s only to experience the engine to quit. The fuel system needs some gravitiy to feed the eng properly. (don't know details, sorry) After some time while gliding for some unknown place in the dark the windmilling prop regenerated a suction flow of fuel to just restart the eng in the last minute... Not really necessary.

Field In Sight
10th Feb 2004, 20:06
It was in a C150 Aerobat without a 'g' meter.

As SquawkModeA said, I made sure that the floating objects did not move towards and then stick to the roof as an indication of the level of acceleration. Also there was no force being provided by the lap straps.

It's a fair point that a 'g' meter would have been better but as I don't think the maneouvre when entered progressively causes negative 'g' it isn't needed.

That was the point of the question to confirm my own understanding of the dynamics of the manoeuvre.

I am sure an aerobat experiences more extreme forces than this when doing aerobatic training.

FIS.

Kerosene Kraut
10th Feb 2004, 20:16
Aerobat sounds just fine.

Bre901
10th Feb 2004, 21:25
Field In Sight

As far as physics and especially dynamics are in question, you are right, all of you, including sandwiches and the spamcan itself were experiencing free fall and the load factor on the airplane was more or less 0 g. And if you went progressively (and I stress that) from pulling to pushing, there is no reason why the load factor would go significantly under 0 g.

If you could have plotted your trajectory, it would have been parabolic.

Nevertheless, as the airplane was in free fall, it was accelerating
at rougly one g, i.e, increasing its vertical velocity by 10 ms/s (20 kts) every second.

This means that your TAS was building up, albeit slightly slower as long as the dive was not too steep.

The main issue in this case would probably be the exit manoeuvre (sp?) hopefully early enough, gentle, and before the ASI was in the yellow arc, not even daring to think of the red line.

747FOCAL
10th Feb 2004, 22:06
Shoot, the stuff we used to do in Mooney aircraft had crap flying all over the place. Never experienced no engine or aircraft problems. Theirs nothing like a Rocket. :E

av8boy
11th Feb 2004, 04:27
...and that was just getting it out of the hangar. They should've seen you on a "stabilized" approach...

Dave

:E