Quoting stall speeds with VG's
 

Was wondering if the wealth of PPrune knowledge would know this.

Let's say an aircraft's stall speed is 50 knots and with Vortex Generators fitted, it becomes 45 knots.

Does this mean that the POH would be modified (in theory) to say 45 knots stall, or are stall speeds identified by a seperate line item in the POH?

From memory as an example I think I heard someone saying a while abck that a Chieftain stall speed varied depending on whether or not VG's are fitted so that made me think there might be an extra line item. I guess I'm wondering if the new stall speed with VG's actually REPLACES the stall speed without them...........?

Normally, if a VG kit is fitted there should be a STC in the POH with the new speeds, and a note that '"if x number of VGs are missing, the orginal POH figures shall be used." This would apply to all new performance figures in the STC.

My understanding is that, yes, it would replace the speeds in the POH until you loose a specific number of VGs

Yes VYSE is changed by the STC and there is a replacement POH , if the kit also puts generators up the fin VMCA will also change.

And it is true the STC will specify how many if any of the individual generators and in what pattern can be missing before the kit just becomes parasitic drag and you revert to the manufacturer POH.

From memory ASI face changed aswell to show changes in stall speeds with flaps up/down at MTOW

Thanks gents, that does help. I'll try and find a reg somewhere to cover myself if required. Being an Experimental type I won't need an STC, just a logbook entry and mods to the POH.

Thanks!

XXX Try this Advanced aerodynamics - Rapidshare Search

And this
http://strategywiki.org/wiki/X-Plane/Developing/PlaneMaker/Airfoils

Chieftains I flew with VG kit had a supplement at the rear of the flight manual as an appendix. It contained the amended speeds, etc.