VG's on light twins
Thread Starter
Joined: Aug 2003
Posts: 3,833
Likes: 2
From: Sale, Australia
VG's on light twins
Some light twins, Piper Chieftain for example, have a gross weight increase when fitted with these after market STC items. I know what VG's do in terms of energising the boundary layer but not sure how it enables a weight increase. What otherwise limiting factor is being enhanced? Many Thanks.
Joined: Oct 1999
Aviation Qualifications: ATPL
Posts: 7,371
Likes: 926
From: Den Haag
I had assumed it was a Stall Speed function, and some research seems to bear this out. I found this article which seems to cover the issues (around page 6/7 I think)
http://cobweb.ecn.purdue.edu/~andris...001/twnvgs.pdf
http://cobweb.ecn.purdue.edu/~andris...001/twnvgs.pdf
Joined: Oct 2007
Posts: 54
Likes: 0
From: Millington
The gross weight increase offered by the VG STC is a direct
result of the reduction in stall speed. Under the FARs, light twins are required to have an engine-out rate-of-climb (in feet/minute) equal to .027 times the square of Vso (in knots). If you lower Vso by a few knots, the required single-engine ROC goes down. At the same time,
result of the reduction in stall speed. Under the FARs, light twins are required to have an engine-out rate-of-climb (in feet/minute) equal to .027 times the square of Vso (in knots). If you lower Vso by a few knots, the required single-engine ROC goes down. At the same time,
Thread Starter
Joined: Aug 2003
Posts: 3,833
Likes: 2
From: Sale, Australia
212man - thanks, its marvellous how you can't see the woods for the trees at times. So obvious. Will have to improve internet skill apparently. Trawled net for info but all I found dealt with resolving aero issues on heavies. But still don't see how it can increase the ZFW.
Nathan - FAR 23.67 details the climb requirements and are based on Vso.
Nathan - FAR 23.67 details the climb requirements and are based on Vso.
Joined: Oct 1999
Aviation Qualifications: ATPL
Posts: 7,371
Likes: 926
From: Den Haag
Nathan, I assume you mean the RoC climb requirement has changed and is now a climb gradient requirement?:
http://rgl.faa.gov/REGULATORY_AND_GU...8?OpenDocument
http://rgl.faa.gov/REGULATORY_AND_GU...8?OpenDocument
Joined: Oct 2007
Posts: 54
Likes: 0
From: Millington
Originally Posted by Brian Abraham
Nathan - FAR 23.67 details the climb requirements and are based on Vso.[
Joined: Nov 2005
Posts: 15
Likes: 0
From: USA
Rate-of-climb
Just an ahah - the requrement for some aircraft (<6000 lbs, reciprocating engines) IAW FAR 23.67(a)(2) is to determine a ROC at 5000 ft., it does not mean the aircraft can climb, this could and sometimes is a minus (decent) number.
Why do it if it's not fun?
Joined: Jul 2001
Posts: 4,782
Likes: 12
From: Bournemouth
I was about start a new thread, linking to a question I've asked in Private Flying. Then I saw this thread, and realised it's very closely connected to my question.
I wonder if I could trouble you to click on this link and add any comments?
Thanks!
FFF
---------------
I wonder if I could trouble you to click on this link and add any comments?
Thanks!
FFF
---------------
