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You are absolutely right about that. From what I can gather, the maximum G rating that one may see in a pilot's manual is the SAFE limit, but the aircraft can be stressed beyond this (maybe up to 20% or more????). If this occurs a thorough inspection of the airframe would be required to see what if any damage resulted from the "Over G" (our A-10s do this on a semi-routine basis).
A pilot must also take into effect IAS, as this effects the maximum allowable Gs. According to the pilot's manual, an F6F-5 Hellcat for example could regularly sustain a +7/-3 G acceleration while flying at approximately 425 mph IAS at 10,000ft, but this drastically changed as the pilot flew higher and higher. Due to changing (or less) air pressure at altitudes above S/L (which in turn effect IAS readings) the same Hellcat would be limited to only +3.5/-3G acceleration at approximately 320 mph IAS at 30,000ft.
I admit to being totally surprised by this, whoever thought that the planes I quoted were so relatively weak. There must be some definition that's wrong. A Tempest was a tough aeroplane but 50% stronger than the most modern aerobatic and combat aircraft around, I just don't get it.
At Culdrose we had an F4 which had pulled G over its limit, I really cannot remember what it was. Wings were twisted, rivets and panels popped, it never flew again, the fact it got back was deemed a minor miracle.
I will now retire to a dark corner
I admit to being totally surprised by this.....
I was too, but that's what Greyman's reference states. Maybe he can give us some more details regarding these stats....
I you check farther down on the Typhoon page you will see some roll rate data for a Typhoon 1a going from 45 degrees one way to 45 the other, averaging just less than 2 seconds at 200 and 300 ASI
From that big (Ministry of Aircraft Production?) chart that was floating around a while ago:
Ultimate Flight Factors (US types are specification factors, not achieved factors)
Hurricane IIc (7600 lb): 10.7 g
Spitfire IX (7240 lb): 10.0 g
Typhoon Ib (11350 lb): 11.5 g
Tempest V (11640 lb): 14.0 g
Tomahawk (6835 lb): 12.0 g
Airacobra (7400 lb): 12.0 g
Thunderbolt (---- lb): 12.0 g
Mustang (7836 lb): 12.0 g
Wow that is interesting and a bit counter-intuitive. Do you know why thinner air or higher altitude made G more risky / damaging for the airframe? Is that just a matter of the TAS?
Hello Slaterat,
On the assumption that "Less than 2 seconds" in this case means around 1.5 seconds:
The roll rate would only be about 60 degrees per second which is quite poor performance and this is not even at high speed.
Just for a performance comparison:
The early P-40 (Probably Tomahawk) had a peak roll rate of 135 degrees per second at 350 MPH IAS.
At 200 MPH IAS, roll rate was around 75 degrees / second
At 300 MPH IAS, roll rate was around 115 degrees / second
(from AHT graph)
The Merlin P-40 seems to be a lot slower for some reason.
(By reputation the P-40 had a pretty good roll rate.)
At 200 MPH IAS, 84 degrees / second
At 300 MPH IAS, 83 degrees / second
(my read of the graph)
Thanks for the data, Greyman,
I wonder what the operational limits actually were because at least for the US types, these are the maximum loads above which the wings are expected to fail. Typically, the US aircraft as originally designed could tolerate up to 8G without permanent structural damage but that limit drops as aircraft weight inevitably grows.
Hello Schweik,
Thanks for the listing of turning times.
I would have thought there would be an advantage for the Soviet Yak fighters, but they look pretty close to even. I am very surprised the lightened Yak-1 did not show a more consistent advantage.
- Ivan.
Well one of the Yak 1s said it turned in 17 seconds which is very fast indeed. The test shown were mostly done at 1,000 ft and at I forget at what speed. It's probably different at different altitudes and speeds without a doubt.
It's also odd that the Hurricane had such bad turn times since most people say it out turned most of the other planes listed. So who knows there could be issues with those tests.
So I wouldn't take it as definitive proof it's just a data point.
From what I read one of the traits of the Yak which isn't that easy to quantify is that they did not lose speed much in a turn (or as much) having small wings they had a lot less drag. So they could turn and keep turning. If that makes sense.
I had no idea about the extent of this either. And look how tough the Tempest is. I think WW2 planes were a bit more heavily built than modern fighters. Most modern fighters (with certain exceptions like the A-10 and the Su-27) don't even have armor any more. Carbon fiber and so on is much lighter but not quite as strong by weight. I think?
I admit I'm out of my depth here so forgive me if I'm wrong about that.
Just for a performance comparison:
The early P-40 (Probably Tomahawk) had a peak roll rate of 135 degrees per second at 350 MPH IAS.
At 200 MPH IAS, roll rate was around 75 degrees / second
At 300 MPH IAS, roll rate was around 115 degrees / second
(from AHT graph)
The Merlin P-40 seems to be a lot slower for some reason.
(By reputation the P-40 had a pretty good roll rate.)
At 200 MPH IAS, 84 degrees / second
At 300 MPH IAS, 83 degrees / second
(my read of the graph)
Hello Slaterat,
On the assumption that "Less than 2 seconds" in this case means around 1.5 seconds:
The roll rate would only be about 60 degrees per second which is quite poor performance and this is not even at high speed.
Just for a performance comparison:
The early P-40 (Probably Tomahawk) had a peak roll rate of 135 degrees per second at 350 MPH IAS.
At 200 MPH IAS, roll rate was around 75 degrees / second
At 300 MPH IAS, roll rate was around 115 degrees / second
(from AHT graph)
The Merlin P-40 seems to be a lot slower for some reason.
(By reputation the P-40 had a pretty good roll rate.)
At 200 MPH IAS, 84 degrees / second
At 300 MPH IAS, 83 degrees / second
(my read of the graph)
I was too, but that's what Greyman's reference states. Maybe he can give us some more details regarding these stats....
No more granularity in the data unfortunately.
I did copy down figures from destruction tests of the Spitfire I, Hurricane I and 109E. Those are much more detailed.
eg Spitfire I (design factor 10.0) 6,200 lb:
High incidence condition
no permanent set at 10.0 Gno serious effect below 11.5 G when rivets begin to failcollapse by fracture of main spar at 12.3 GLow incidence condition
no effect other than waving skin up to 9.0 Gcollapse by failure of skin attachment at 12.0 G
Wow that is interesting and a bit counter-intuitive. Do you know why thinner air or higher altitude made G more risky / damaging for the airframe? Is that just a matter of the TAS?
Close. At higher altitudes you generate less lift for a given airspeed and sustain it for less time due to engines making less power.
Well one of the Yak 1s said it turned in 17 seconds which is very fast indeed. The test shown were mostly done at 1,000 ft and at I forget at what speed. It's probably different at different altitudes and speeds without a doubt.
It's also odd that the Hurricane had such bad turn times since most people say it out turned most of the other planes listed. So who knows there could be issues with those tests.
So I wouldn't take it as definitive proof it's just a data point.
From what I read one of the traits of the Yak which isn't that easy to quantify is that they did not lose speed much in a turn (or as much) having small wings they had a lot less drag. So they could turn and keep turning. If that makes sense.
Ivan1GFP said:Hello Schweik,
That Yak-1b (predecessor of the Yak-3) was the lightened Yak-1 I was referring to.
Note though that its times were not consistent.
They probably all started out at cornering speed.