View Full Version : Why does the IVSI show an initial climb when turning?
akafrank07
7th Dec 2012, 15:25
"The disadvantage of an IVSI is that the dashpots, which sense the vertical acceleration of the aircraft, are also affected by the acceleration in a turn. Therefore, the IVSI has an error that it initially shows as a rate of climb when applying large angles of bank, i.e., over 40 degrees of bank. However, if the turn is maintained, IVSI will stabilize to zero but then indicates a rate of descent as the aircraft rolls out of the turn."
Why are these affected by acceleration in a straight and level turn and not affected by normal acceleration? and why is it that it happens over 40 degrees of bank?
Thnaks
packo1848
7th Dec 2012, 18:02
The accelerometers in the IVSI sense acceleration in the aircraft vertical only. As you enter a turn you have to increase lift to account for the portion of lift now acting towards the centre of the turn; an acceleration in the vertical plane.
By 'normal' acceleration, I assume you mean an increase in speed? Which is an acceleration along the longitudinal axis, the accelerometers in the IVSI aren't aligned to sense on this axis, so no climb/descent is displayed.
As for why only above 40 degrees of bank, I can only guess that maybe the instrument is calibrated for the smaller bank angles used in normal flight.
Lightning Mate
7th Dec 2012, 18:28
Oh fcuk, here we go again with more moronick ill-informed ****!!!!
packo1848
7th Dec 2012, 18:38
How moronic and ill-informed?
Apologies if I got that wrong, I am merely passing on what I've been taught, in an attempt to help. I'm by no means a subject matter expert and would never pretend to be. Would you care to give the correct explanation so i can no longer be a 'moron' or 'ill-informed'?
Thanks.
Lord Spandex Masher
7th Dec 2012, 19:10
I think he might when he sobers up ;)
packo1848
7th Dec 2012, 19:19
Suspected maybe as much with similar posts on other threads. :}
Nearly There
7th Dec 2012, 20:12
Jesus wept, a guy asks a question which in real life people would answer and if two or more answers arise a discussion starts......why is pprune so different? just full of keyoard warriors, if you've nothing decent to say why click reply lightning mate?
akafrank07 is 22 and trying to find out something he doesn't know. He will make a good pilot if he carries on with this attitude. Well done mate, and well said packo.
I suggest LM's very rude post is against Pprune rules.
.
Halfwayback
7th Dec 2012, 21:55
He has a week to think about it!:rolleyes:
HWB
akafrank07
7th Dec 2012, 23:02
Thanks for the reply packo thats clarified it for me :ok:
The main question arising from this would be who is doing turns greater than 40 degrees AOB on instruments? Every company policy would be 30 max.