Wing 'Safety Tips'

[tcasblue]

Have you ever heard of them. Have been reading about the Grumman Bearcat which had them and was wondering if any other types did.

"The wings of the early F8F were provided with 'Safety Tips', designed to fail when the wings were inadvertently overloaded in flight, thereby resulting in an aircraft with reduced span and greater ability to withstand high flight loads.

Because of fatal accidents, resulting from violent uncontrolled motions after loss of only one of the wingtips, a wing jettisoning device was developed for service installation and was intended to ensure that when one wingtip failed the other wingtip would be shed explosively, immediately after the initial tip failure. The safety wingtip feature was eventually eliminated because of the impossibility of making and maintaining a continuously reliable installation of the explosive wingtip shedding device in service aircraft."

[DaveReidUK]

Where did you read that ?

Did it really refer to "violet uncontrolled motions" ? :O

[Goldenrivett]

Hi tcasblue,

Wikipedia (https://en.m.wikipedia.org/wiki/Grumman_F8F_Bearcat) has a good explanation.

”Another weight-saving concept the designers came up with was detachable wingtips. The wings were designed to fold at a point about 2⁄3 out along the span, reducing the space taken up on the carrier. Normally the hinge system would have to be built very strong in order to transmit loads from the outer portions of the wing to the main spar in the inner section, which adds considerable weight. Instead of building the entire wing to be able to withstand high-g loads, only the inner portion of the wing was able to do this. The outer portions were more lightly constructed, and designed to snap off at the hinge line if the g-force exceeded 7.5 g. In this case the aircraft would still be flyable and could be repaired after returning to the carrier. This saved 230 pounds (100 kg) of weight.”

[tcasblue]

DaveReidUK

Correction made to violent.

I have been reading some books by Eric Brown about some of the aircraft he flew and have a list of terms and features to ask about that I found particularly interesting.

It sounds like it was designed at the folding wingtip which makes sense.

I am curious if any other aircraft might have had the Safety Wing Tip feature.

[B2N2]

Somehow I don’t think they were designed as safety tips more convenient engineering for the folding wing.
Can you imagine the upset if one failed ?
Then the solution of blowing off the other one
:mad:

[megan]

It sounds like it was designed at the folding wingtip which makes sense

I am curious if any other aircraft might have had the Safety Wing Tip featureThe point of detachment was three feet in from the tip, had it been at the wing fold you would have had no ailerons, the wing fold was six feet inboard of the tip, not a feature of any other aircraft that I'm aware of.

You can read of test pilot Corky Meyer's testing of the wing tip feature in his book "Flight Journal", a disjointed account here.

https://books.google.com.au/books?id=uAXLBAAAQBAJ&pg=PA143&lpg=PA143&dq=Clipping+the+Bearcat%27s+wing&source=bl&ots=KxB3Kxb4uA&sig=ACfU3U0DK8hX2BCqlrZ-tBBx1rjnjoRCIg&hl=en&sa=X&ved=2ahUKEwjuxMrxotXyAhUPlEsFHQozCXQQ6AF6BAgyEAM#v=onepage&q=Clipping%20the%20Bearcat's%20wing&f=false

[tcasblue]

OK, I ordered the book and read that chapter. I think the whole overall point of the safety tips was to save weight by having less structure in the outer wing tips. The wings were designed to what I would call.....having two ultimate loads, one at 7.5g that would break off the outer portions at a controlled location(at a carefully designed rivet joint at half span of the outer, folding part of the wing). This also broke off the outer half of the aileron(as designed).

Once the outer portion of the wings(3 feet) broke away, the wing was relieved of tip loads and the remaining portion was good to its second ultimate load of 13 g.

A higher approach speed was required when this happened but the aircraft was still landable on a carrier.

[megan]

I think the whole overall point of the safety tips was to save weight by having less structure in the outer wing tipsAs the aircraft was designed for the interceptor role weight saving was sought to maximise the rate of climb, the savings came by being able to reduce the size, and hence strength, of the spars etc inboard of the detachable portion, the detachable wing tips reduced the leverage being applied to the inboard/wing root areas. The weight savings was given as 230 pounds. The aircraft was 2,000 pounds lighter and had a 30% higher climb rate than its predecessor Hellcat despite using the same engine.

[tcasblue]

I believe that is the final piece of the puzzle and not specifically mentioned in the book. The detachable wingtips enabled a lighter construction of the inner portion of the wing(and quite possible outer as well) saving weight while still allowing the maximum g-load rating requirement to be achieved(just with a little less wing and aileron).

A picture of the detaching/detached wing would be nice.

Thanks

[DuncanDoenitz]

Maybe I'm just being thick, but is it the light-weight centre wing structure, the frangible outer wing panels, the self-severing ailerons or the ability to explosively-jettison the wing-tips which justify the epithet "safety"?

[megan]

Certainly, the detachable wing tips allowed for a lighter structure, enhancing rate of climb, and by detaching avoided over loading the structure. That was the theory.