Why is it important for wing tips to stall last on an aircraft wing? And do all ultralights have it?

[facthunter]

A normal light plane without any washout would be less efficient than with it. You only need all the wing you have at slow speed, and as you increase speed the AoA decreases for the whole wing. The outer wing will create less wing tip vortices, due to the washout, it's not producing (much, any) lift. The inner wing can provide the lift needed. Nev

 

 

[eightyknots]

Solomon, Seeing as no one has directly spoken about wing planforms and the stall tendencies of each, and because I assume you are now wondering about wing washout for your homebuilt as a result of posts in this thread, I will briefly brush over it. Not all planes need washout! A good example of a plane with zero washout that has thousands flying safely are RV's, they use a 'hershey bar' wing planform, which is basically a rectangle; a 'hershey bar' wing does not necessarily need washout as it tends to stall around the root and progress out leading to a fairly stable stall. A picture tells a thousands words, See diagram:

 

I'll just copy this from Wikipedia about the Piper PA-28 which also originally had a 'Hershey Bar' wing planform and it talks about washout:

 

Now, by no means am I an engineer, I am sure there are some qualified aircraft engineers out there who will be able to explain this further in depth with you, how ever I highly suggest before you make any changes to your aircraft in regards to this topic:

 

Get an aircraft engineer to look over your design and build progress, get him or her to explain the designs, get him or her to do the figures and to ensure everything is as it should be for a safe stable design, and most of all, get him or her to help you decide if your particular design needs any of these features or changes.

I suppose the Savannah has the Hershey Bar wing and may explain the reason that it appears to lack other 'devices' to ensure the wingtips stall last.

 

If RAA was able to produce accident reports (as in, if they could get the police report and publish the relevant aviation facts) we would all know because one did fall out of the sky from 300' with two experienced pilots in it, who fortunately survived. If they read this, they might like to make a comment on whether (a) the wings had slats, (b) the slats had been removed, but no VG's fitted, © the slats had been removed and VG's were fitted.

I have never heard of this incident T-P. Perhaps someone has more information about this, e.g., did the Savannah involved have slats or VG or did it have the ADV wings?

 

 

[68volksy]

Old Mr Piper new what he was doing and kept it so very simple! The Warrior tends to stall with a great deal of aileron effectiveness still remaining and would certainly never resort to dirty tricks such as dropping a wing! One accepted stall recovery technique is simply letting go of everything and then picking it up when it's flying again. Tends to lose a little more height than the usual recovery though...

 

It's certainly a good slab of rectangular wing on the Savannah - a couple of the guys at the flying school have built them over the years. Talking stalls with them was very similar to the Warrior stalls. Mind you they were talking almost taxi speeds for the stall speed. There was a degree of caution though as if the wings are screwed on at slightly different angles (see your average Cessna?) they will drop a wing in the stall. Due to the low stall speed this had the potential for a good deal of height loss. Only hearsay mind you - never flown in a Savannah.