FLYBOYJ
"THE GREAT GAZOO"
If you watch the video I posted you'll see the uneven airflow off the wing at higher Mack number eliminates elevator control. The start of the shock wave at speeds approaching Mach 1 starts at the wing (leading edge).
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If you watch the video I posted you'll see the uneven airflow off the wing at higher Mack number eliminates elevator control. The start of the shock wave at speeds approaching Mach 1 starts at the wing (leading edge).
Any mail?Leaving. I have to go to the post office anyway.
Paying bills.
I mean this, in the red square:I don't know what you think you are discerning from the table above. Calculate value for M as function of altitude = 33.42*Sqrt (R) where R= degrees Rankin for each Altitude (on right). Divide the TAS (i.e. 495mph TAS @40,000 feet) by the calculated local Speed of Sound(M). R=390.0 at 40K. M= 1.0 at 659mph at 40K.
IAS limit at 495mph IAS = 495/659 = .751 Mach.
ALL the TAS values from 40,000 to SL are 0.74-.75M Limit Dives - same as P-51, P-51A, P-51B, P-51C, P-51D, P-51K and about the same as the P-51H which very slightly higher.
The Dive limits of P-47C, P-47D, P-47M, P-47N same as P-51s
You are mis-interpreting the P-51 chart on the right. The Max Permissible (not the same as Possible) Dive (Speed) Limit from 40000 feet to SL is 0.75M. Period. The red vertical line is just that but NAA in its infinite wisdom did not extend the Dive Limit curve from 8,000 feet AGL to SL, as the chart presented is to show the pilot how much altitude he has remaining before he becomes a smokey hole in the ground.I mean this, in the red square:
from sea level to 10,000 ft,
P-47D-30 IAS limit is 500 mph
P-47N IAS limit is 482 mph at 10,000 ft, 522 mph at 5,000 ft and 564 mph at sea level
P-51H IAS limit is 495 mph at 8,000 ft, 505 mph at 4,000 ft and 505 mph at sea level
So dive limit
P-47N > P-51H > P-47D-30
That what very confusing for me, if go to wing design then it shouldn't it be: P-51H >P-47N > P-47D-30
View attachment 652473
The red vertical line is just that but NAA in its infinite wisdom did not extend the Dive Limit curve from 8,000 feet AGL to SL, as the chart presented is to show the pilot how much altitude he has remaining before he becomes a smokey hole in the ground.
I still don't get it, how can they have the same dive capability?1. The P-47D and N Operating Limitations of M=0.75 are the same as P-51B/D and H.. The difference between the two is that the P-47 when exceeding the Dive Limit experienced 'pitch down' moment as transonic to supersonic transition on the top of the wing moved the Center of Pressure (lift) to the rear (same of all fighters except P-63 and P-51). That experience of pressure movement was extremely serious for P-38 which occurred ~ 0.65-69M and required installation of dive flaps for both the P-47D-30 and P-38J-15 (kit), -25 (production.
I still don't get it, how can they have the same dive capability?
For example: in the green box.
At 30,000 ft, P-47D-30 is limited to 250 mph IAS / P-47N is limited to 318 mph IAS / P-51D is limited to 330 mph IAS
At 25,000 ft, P-47D-30 is limited to 300 mph IAS / P-47N is limited to 360 mph IAS / P-51D is limited to 360 mph IAS
At 20,000 ft, P-47D-30 is limited to 350 mph IAS / P-47N is limited to 400 mph IAS / P-51D is limited to 400 mph IAS
At 15,000 ft, P-47D-30 is limited to 400 mph IAS / P-47N is limited to 442 mph IAS / P-51D is limited to 440 mph IAS
At 10,000 ft, P-47D-30 is limited to 450 mph IAS / P-47N is limited to 482 mph IAS / P-51D is limited to 480 mph IAS
At 5,000 ft, P-47N is limited to 522 mph IAS/ P-51D is limited to 505 mph IAS
So it look like at high altitude
P-51D > P-47N > P-47D-30
At medium altitude
P-51D = P-47N > P-47D-30
At low altitude
P-47N > P-51D > P-47D-30
View attachment 652607
Hmm, but the zero lift drag coefficient is still just a coefficient, you can have lower coefficient yet higher total drag though.I fail to understand why you find this surprising or counterintuitive, as dive limits have nothing to do with perceived cleanness of an airframe. Also, to put things in perspective, the P-47 was a lower-drag airframe than several V-12 powered, single-engine fighters, e.g., the Bf109. If one bothers to look up the data, the zero-lift drag coefficient, the only sensible measure of relative "dragginess" of an airframe, does not show a statistically different mean between radial-engine and V-12 engine fighters. The P-51's zero-lift drag coefficient was massively lower than any other WW2 piston fighter; the P-47 was somewhere in the middle of the soup of all the single-engine fighters.
I guess the issue here is with how I phrase my question/opinion since English isn't my mother tongue so might be something is loss with translation.Never-exceed airspeed is not determined by perceived aerodynamic cleanliness. Maximum attainable speed in a dive would be somewhat correlated to weight divided by (wing area times zero-lift drag coefficient), but that's a different parameter and one which doesn't tend to be put in things like operating manuals because Vne will almost always be lower, which means that achieving the maximum possible dive speed is, at best, highly inadvisable and, at worst, is likely to be fatal.
You are getting lost in numbers. 5,000ft is slightly less than a mile/1.6KM. In a 45 degree dive at 505mph IAS calculate the time taken to hit the sea. In many places in the world an altitude of 5,000ft is below ground level. Reno races are at a ground level of 4,500 ft this is less than the average altitude of Nevada which is 5,500ft.At 5,000 ft, P-47N is limited to 522 mph IAS/ P-51D is limited to 505 mph IAS
True. Drag Coeffient(s) for Parasite Drag are functions of Wing Area. In most examples of WWII aircraft the Wing dominates, followed by Fuselage.Hmm, but the zero lift drag coefficient is still just a coefficient, you can have lower coefficient yet higher total drag though.
Like for example: a Mig-31 likely has lower zero lift drag coefficient than a Fokker Dr.I but the total drag of Mig-31 is still bigger since it is much more massive
So, while P-47 drag coefficient probably lower than BF-109, i actually doubt that the actual drag is also lower
Good as such is Unknown with precision during Design. Failure in dives is most often due to dynamic Pressure loading - which is a function of Velocity and local density of air - for which a 'wall' is shown on the Vne diagram, representing the airframe manufacturer's Limit Loading. If the airframe in question has been analyzed part by part for Stress on each part for the limit before Yield point (or established stress/strain curve for the material), then the collective values forlevel flight, dive, manuever are presented in graphic form as a "Vne Diagram". Vne Diagrams are calculated for a specific Gross Weight and 'allowable' or 'limit' G load at THAT Gross Weight. The outer 'Envelope' on a Vne Diagram - composed on Ultimate G load in which an airframe/or components of the airframe exceed elastic stress and enter into 'Fracture/fail/crush/break' zone.I guess the issue here is with how I phrase my question/opinion since English isn't my mother tongue so might be something is loss with translation.
When I asked about dive limit, I don't mean the absolute maximum speed that the aircraft can't excess.
You need to craft a very sophisticated model in which a.) ALL your drag components for Parasite drag are known and you have the 'near correct' equation derived in wind tunnels to expresss CD total as a function of RN. RN will change as the modeled aircraft pitches over, accelerates, increases velocity, changes density due to loss of altitude, changes kinetic viscosity.I mean the maximum speed which it can achieve at certain altitude in a dive (may be there is a word for this?)
So, for example:
Let say a P-47D and a P-51D both flying at 30,000 ft.
Then let say the P-47D somehow able to get behind the P-51D, so the Mustang pilot dive down to 10,000 ft and the P-47D pilot follow him.
Since, P-51D speed limit at 10,000 ft is 480 mph IAS while P-47D limit is 450 mph IAS, that mean P-51D can potentially out dive the P-47D and run away?
That the sort of question i'm trying to answer
Dimensionless coefficients are the only sensible way of comparing aircraft of different sizes.Hmm, but the zero lift drag coefficient is still just a coefficient, you can have lower coefficient yet higher total drag though.
Like for example: a Mig-31 likely has lower zero lift drag coefficient than a Fokker Dr.I but the total drag of Mig-31 is still bigger since it is much more massive
So, while P-47 drag coefficient probably lower than BF-109, i actually doubt that the actual drag is also lower
I guess the issue here is with how I phrase my question/opinion since English isn't my mother tongue so might be something is loss with translation.
When I asked about dive limit, I don't mean the absolute maximum speed that the aircraft can't excess.
I mean the maximum speed which it can achieve at certain altitude in a dive (may be there is a word for this?)
So, for example:
Let say a P-47D and a P-51D both flying at 30,000 ft.
Then let say the P-47D somehow able to get behind the P-51D, so the Mustang pilot dive down to 10,000 ft and the P-47D pilot follow him.
Since, P-51D speed limit at 10,000 ft is 480 mph IAS while P-47D limit is 450 mph IAS, that mean P-51D can potentially out dive the P-47D and run away?
That the sort of question i'm trying to answer
Is that like rigidly defined boundaries of uncertainty?Dimensionless coefficients are the only sensible way of comparing aircraft of different sizes.
The elevator is connected to the stabilator which, in turn, is connected to the fuselage which, in turn, is connected to the wing. If the elevator is going 505 mph, so is the wing and hte rest of the airplane except for the prop, which is likely going faster as it spins.
The Thunderbolts were fast at high altitudes because of their turbochargers. They were replaced with Mustangs partially because their wings suffered more from compressibility. The Spitfires had very high critical Mach numbers because they had thin wings.I cannot find the source (of course) but reputedly the elliptical wing was optimized for high altitude performance, which explains the Spit and P-47 configurations.
First I heard of it was from a Canadian ace who knew A LOT about A LOT. The late Rod Smith.