Lear 45 Delta Fins??

[McDuff]

Someone I know is about to try to get a job on Lear 45s, but he has asked me what the delta fins are for. I reckon that they're there for directional stability, but that the full area would not be available with a ventral fin without making it too big for ground clearance in the flare.

Are there any other smarter ideas around?

cb

[JimmyTAP]

I'm sure I read somewhere years ago that they are angled to provide a pitch down moment at high incidence, thereby getting rid of the stick pusher.

JT

['India-Mike]

Concur with JimmyTAP. I use this aeroplane as a stab&control example with undergraduates. I recollect from a Flight International article years ago that they were to provide a pitch-down moment at high alpha. But they're bound to contribute sideforce and hence yaw moment as well.

[McDuff]

Concur with JimmyTAP. I use this aeroplane as a stab&control example with undergraduates. I recollect from a Flight International article years ago that they were to provide a pitch-down moment at high alpha. But they're bound to contribute sideforce and hence yaw moment as well.

Thanks chaps, that's most useful (and interesting). But do you mean to reduce the sideforce or provide one? Surely the delta wings would add to the keel surface and therefore directional stability?

cb

[Mad (Flt) Scientist]

LearJet Delta Fins (http://www.pprune.org/forums/showthread.php?t=225806)

specifically the last post