RedFlyer From United States of America, joined Feb 2005, 4316 posts, RR: 28 Posted (8 years 6 months 2 weeks 4 days 20 hours ago) and read 6685 times:
I noticed on 737NGs (haven't flown the classic recently to notice) that there are stall strips on the leading edge of the wing just inboard of the engines in the same area where the Krueger flaps are. I know the purpose of the stall strips is to make that part of the wing (inboard) stall before the rest of the wing (outboard) to ensure control is maintained by the ailerons throughout the stall regime. However, I also noticed that when the Krueger flaps are deployed that they cover the stall strips.
So, my question is, how is control maintained by the ailerons if the wing stalls when the leading edge flaps are deployed? Are the dimensions of the flaps (both krueger and extender type) such that the inboard portion of the wing will still stall before the outboard section of the wing?
OldAeroGuy From United States of America, joined Dec 2004, 3490 posts, RR: 66
Reply 1, posted (8 years 6 months 2 weeks 4 days 5 hours ago) and read 6591 times:
The stall strips are for flaps up stall characteristics.
Flaps down, the Krueger does not delay stall for the inboard wing as well as the slat does for the outboard wing. Therefore it doesn't matter that the Krueger covers the stall strip when it deploys.
The result is that for with either clean wing or flaps down, the inboard wing stalls first, producing good stall characteristics, ie the nose pitches down at stall because the inboard wing stalls first.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis