Hi,What's the purpose of this gadget mounted on the centerpost of the BAe-146? There seems to be a similar thing on the A320, and others.A pic:http://www.airliners.net/open.file/273384/M/Anybody know this one?Thanks!Greghttp://www3.sympatico.ca/gregory.moffatt/DHC-8_profile.jpg

Don't know, but it looks like it is connected to the dooma-flotchy, which is mounted to the whatchamacallit! ;-)Darrell

Airlines attempt at fuzzy dice?- insert your favoite quote from the movie Airplane -

buncha jokers...and don't call me Shirleyhttp://www3.sympatico.ca/gregory.moffatt/DHC-8_profile.jpg

Is it some type of compass calibration instrument?Brent Hebert

My guess is that its for level flight, kinda like those balance things with a bubble, but then again, I may be wayyy offJay

I am not sure as to what the "Official" name is but they are used for the pilots to adjust their seat "Height" so they have the "Correct" sight picture down the runway. I believe they set the indicator at eye level and then they are good to go.Terry

The oficial names are "balancing balls" or "compensation balls".Brent Hebert

Well there you go -- another mystery solved. That makes perfect sense...Thanks,Ghttp://www3.sympatico.ca/gregory.moffatt/ERJ_CRT.jpg

Well, who ever said that they are for adjusting the pilot's line of sight is correct...ie, seat position.The way they work is to eclipse the far yellow ball with the center black ball thus putting the pilots head in the proper position.Most of the heavy aircraft operating manuals have a page devoted to the proper adjustment of the seats. On the 757 which has no balls (Don't go there) you sight down the top of the glare sheild and place the top of the yoke hub in-line with the bottom point of the lower nav display CRT.In fairness, the balls do look like compensating balls found on the maritime ships compass used to adjust (or swing) the ship's compass to deaden out the effect of the ships hull. On the planes we have compass cards (Don't leave the ground without it)..Tim_757

It sure would be great to have something like this in cars. It always seems to take a week or two to adjust my seat after in comes back from the dealer. This past time, the lot driver was sitting in the back seat when he brought the car around to the pick up zone.Terry

It is an interesting device -- very simple too. Thanks for clearing that one up for me. You have to admit -- simming is a very educational hobby. I'm not a pilot (not yet anyways), but I must be way ahead of the general public on the subject of aviation.Here's a follow up for you, if you don't mind -- what's on a compass card? I think they show the magnetic heading / true heading for 0, 45, 90, etc. Am I close?http://www3.sympatico.ca/gregory.moffatt/ERJ_CRT.jpg

Greg,For a given cardinal or inter-cardinal heading the card just shows the difference between the magnetic compass reading and the actual magnetic heading, in tabular form. The difference is established by doing a "compass swing" on an aircraft. This involves aligning the aircraft along known headings on the ground, adjusting the compass as required (with the little plus and minus screws) and tabluating what the eventual differences are (you cannot get them all bang on for all headings). Usually it is only a deg or two difference and can just be ignored for practical purposes. The card is displayed in close proximity to the mag compass.Kevin in CYOW