Tu-22 down in Murmansk, 2 fatalities

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jimdavis
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Re: Tu-22 down in Murmansk, 2 fatalities

Unread post by jimdavis » Mon Jan 28, 2019 10:47 pm

heisan wrote:
Mon Jan 28, 2019 12:23 pm
That may be true for fighters. Bombers typically have much lower G ratings - especially when loaded. For example, the closest US equivalent would probably be the B-1B, which has a G limit of 2.8G with full load.
Justin, would it be normal for civilian light aircraft to have different G load limits at different weights? Something doesn't sound right there. I haven't ever seen it published in aircraft handbooks.

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heisan
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Re: Tu-22 down in Murmansk, 2 fatalities

Unread post by heisan » Mon Jan 28, 2019 11:10 pm

jimdavis wrote:
Mon Jan 28, 2019 10:47 pm
heisan wrote:
Mon Jan 28, 2019 12:23 pm
That may be true for fighters. Bombers typically have much lower G ratings - especially when loaded. For example, the closest US equivalent would probably be the B-1B, which has a G limit of 2.8G with full load.
Justin, would it be normal for civilian light aircraft to have different G load limits at different weights? Something doesn't sound right there. I haven't ever seen it published in aircraft handbooks.

jim
The good old Cessna 172 is an easy example. Can be operated in 'normal category' @2400lbs MAUW, with a load limit of 3.8G. Or 'utility category' at 2100lbs MAUW, with a load limit of 4.4G.

Military aircraft have much more restrictions with various load limits based on which fuel tanks are full, or which stores are fitted.

IIRC some WWII bombers took off with a 1.5G manoeuvring load limit - but burnt off enough fuel to at least have some margin by the time they were over the target.
Justin Schoeman

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jimdavis
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Re: Tu-22 down in Murmansk, 2 fatalities

Unread post by jimdavis » Tue Jan 29, 2019 7:23 am

Thanks so much Justin. You are right of course. I had forgotten all about the the normal and utility categories.

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Re: Tu-22 down in Murmansk, 2 fatalities

Unread post by Dragon » Thu Jan 31, 2019 10:23 pm

Landing G limitations and flying G limitations are two completely different things.

For flying one is primarily interested in the wing bending moments, esp for positive G the ability of the wings to support the weight of the fuselage. Thus it is their ability to resist bending upwards to put it crudely. For the fuselage it would be its ability to hang from the wings without bending or breaking off.

For landing, one is primarily interested in the wing bending moments as they flex downwards (opposite direction to flying G considerations) as the wheels impact and accelerate the aircraft upwards while the wings are still descending. For the fuselage one is also looking at how its downward inertia copes with the upward acceleration coming from the wheels wherever they might be placed. So here it is the wheels doing the lifting instead of the wings, but the effect on the surrounding fuselage will be similar to the flying situation (it will want to bend downwards). There are obviously other landing gear structures that will have limits that also come into play.

Because of the differences, these limitations do share a vague relationship with regards to the fuselage, but are sufficiently different That the manufacturer sets different limits for them.

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