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PacificBeach88
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True Max Speed Of 747/VC25

Sat Sep 10, 2016 1:09 pm

To you 747 drivers out there, what is the true max speed of a 747? On wiki and other sources it lists it as mach .89. In this article about 9/11 Col. Tillman admits he was going mach .94 and the F16s were having a tough time catching up with Air Fore One that day without using afterburners. He also admits to being at FL45 which seems within spec. Any thoughts or comments?

http://www.politico.com/magazine/story/ ... sky-214230
 
mmo
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Re: True Max Speed Of 747/VC25

Sat Sep 10, 2016 1:54 pm

Max alt for the 200 is FL451. It can certainly do .94, but you will have the overspeed warning, unless you pull the C/B.
 
b747400erf
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Re: True Max Speed Of 747/VC25

Sat Sep 10, 2016 2:28 pm

You cannot find reliable specs for the VC-25
 
RW01MIA
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Re: True Max Speed Of 747/VC25

Sat Sep 10, 2016 2:36 pm

PacificBeach88 wrote:
To you 747 drivers out there, what is the true max speed of a 747? On wiki and other sources it lists it as mach .89. In this article about 9/11 Col. Tillman admits he was going mach .94 and the F16s were having a tough time catching up with Air Fore One that day without using afterburners. He also admits to being at FL45 which seems within spec. Any thoughts or comments?

http://www.politico.com/magazine/story/ ... sky-214230


A fair question but comparing apples to oranges somewhat. The VC25 is based largely on the 747 design, but is a very modified aircraft throughout. While you can compare its handling and performance specifications to a factory-build commercial 747, there are design and operational factors which impact the performance of the airframe. The ability to refuel midair allows the aircraft to fly slightly higher and faster than other 747's as the operating weight is substantially decreased.

You'll not be able to find accurate performance numbers for the aircraft. Anything online is pure conjecture and 747-200 specs are way off the mark. The actual performance characteristics of the airplane is classified. None of the a.net armchair aviators have a clue.

Good question.
 
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flylku
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Re: True Max Speed Of 747/VC25

Sat Sep 10, 2016 3:57 pm

I worked with someone who was a Flight Engineer on the VC25 during acceptance testing. He said they got it as slow as 95 knots and slightly above mach 1.

I was speaking to an FO on the 747-400 and he said once on a trip to NRT they had plenty of fuel and the only reason they could not do mach .95 is the FMS would not accept it. I think they were bored and only did this briefly.

I went to to business school with a former A-6 pilot and squandron commander who had a friend who was involved in flight tests on the 747 (he was stationed out at Whidbey Island so it would make sense that he might come in contact with Boeing pilots). He was told the 747 has no trouble exceeding mach 1.0. I think it voids the warranty though.

I think the big issue is control surface lock. The fusealage has a bit of a coke bottle shape and so in some ways conforms to the area rule.

If true, the 95 knot number is the one that is truly astounding.
 
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PacificBeach88
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Re: True Max Speed Of 747/VC25

Sat Sep 10, 2016 4:17 pm

RW01MIA wrote:
You'll not be able to find accurate performance numbers for the aircraft. Anything online is pure conjecture and 747-200 specs are way off the mark. The actual performance characteristics of the airplane is classified.


That's why I was surprised both Col Tillman and the F16 driver mentioned mach .94 for the VC25. I know in flight testing for brief periods of time in descents and similar the 747 has come close to or slightly exceeded mach 1. But the fast cruise number surprised me. It made me wonder what the airframe is actually capable of if need be at a given flight level. Thanks for your input.
 
kalvado
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Re: True Max Speed Of 747/VC25

Sat Sep 10, 2016 4:19 pm

flylku wrote:
I went to to business school with a former A-6 pilot and squandron commander who had a friend who was involved in flight tests on the 747 (he was stationed out at Whidbey Island so it would make sense that he might come in contact with Boeing pilots). He was told the 747 has no trouble exceeding mach 1.0. I think it voids the warranty though.
.

I think that was about China Airlines 006 which is estimated to go above M1.00. And, besides some pax injured by high g-forces, there were a few small problems with the frame, like wing getting permanently bent and a good chunk of stabilizer missing..
 
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PacificBeach88
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Re: True Max Speed Of 747/VC25

Sat Sep 10, 2016 4:24 pm

flylku wrote:

If true, the 95 knot number is the one that is truly astounding.


That would be astounding. I guess that would make the plane pretty flexible for in-flight refueling, which makes me wonder if the VC25 pilots ever practice that on the VC25s or if they practice using the E4s instead? Or is that a simulator exercise only?
 
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TWA772LR
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Re: True Max Speed Of 747/VC25

Sat Sep 10, 2016 4:56 pm

PacificBeach88 wrote:
flylku wrote:

If true, the 95 knot number is the one that is truly astounding.


That would be astounding. I guess that would make the plane pretty flexible for in-flight refueling, which makes me wonder if the VC25 pilots ever practice that on the VC25s or if they practice using the E4s instead? Or is that a simulator exercise only?

I'd imagine the 95 kts speed is more for short field landing performance. KC135s and KC10s would have no problem staying with the VC25 at normal cruise speeds.
 
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RetiredNWA
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Re: True Max Speed Of 747/VC25

Sat Sep 10, 2016 5:54 pm

There was an Evergreen (cargo) 747 Generic (747-100) that exceeded Mach 1.0 for a very brief period of time back in the early 1990's due to an uncommanded roll event. I am not 'Google' savvy, so someone out there could probably find information and link it to you.

No VC25 aircraft would refuel at 95 knots IAS. Airborne refueling is a complex series of events requiring the ability to safely detach and recover an aircraft - at altitude - with airspeed - should some abnormal situation occur. Considering the optimum altitudes for airborne refueling for this aircraft type are in the 18,000 to 36,000 foot range (FL180-FL360) and the inability of a KC-130, KC-135 or KC-10 tanker aircraft to maintain such a slow airspeed in constant, level, at altitude flight, this is a moot point. Low and slow flight in aerial refueling is not an optimum situation. It would require high thrust settings, lots of lift devices thrown out into the airstream (think landing configuration flaps minus deployed landing gear) and it would be grueling for the pilots involved.

Is part of your question "could" or "would" the 747 airframe attain Mach 1.0 and keep flying? If so, the answer is yes - for a brief period of time. Operating transport category aircraft at or above Mach 1.0 is not sustainable. The enormous stress put on the airframe and control surfaces would almost certainly lead to an in-flight structural failure of some sort. If memory serves me correctly, the Evergreen International incident I referenced in the first part of my response ended safely but not without substantial damage to the airframe. You can also reference the China Air Lines 747SP engine failure-uncommanded roll-dive event in the 80's for a better understanding of the G-forces required to control an aircraft in that speed regime and attain (or maintain) level flight.

Air Force One is not routinely operated in a high speed regime near the speed of sound. A basic understanding of aerodynamics, such as "Coffin Corner" or "Q-Factor" (the 'aerodynamic ceiling') would bring you to this conclusion: Yes, the 747/VC25 CAN fly at Mach 1.0 - but not for long.

-RetiredNWA
 
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dlednicer
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Re: True Max Speed Of 747/VC25

Sat Sep 10, 2016 11:33 pm

According to the FAA Type Certificate Data Sheet, Mmo of the 747-200 is M=0.92. As it is an older, pre-amendment 25-91 airframe, you can figure that Mdive is 0.05 greater (M=.97).
 
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Spacepope
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Re: True Max Speed Of 747/VC25

Sun Sep 11, 2016 1:59 am

mmo wrote:
Max alt for the 200 is FL451. It can certainly do .94, but you will have the overspeed warning, unless you pull the C/B.


Well, sorta. Civilian ones are restricted to 451 because of the time it takes to get down to 10000 feet. Military ones aren't restricted like that, and we used to have a 747 driver on this forum a long time ago that claimed the E-4s during ODS regularly operated above FL500
 
spacecadet
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Re: True Max Speed Of 747/VC25

Sun Sep 11, 2016 6:22 am

"Maximum speed" is a moving target, for any aircraft. It depends on a lot of things. A lot of aircraft can go faster than their listed max speed for a given altitude, but they're not rated for it because of stresses on the airframe. But it's not like they'll hit mach .92 and suddenly stop accelerating like they've hit a brick wall; the pilot is meant to stop accelerating at that speed. It's kind of like how a lot of cars in the 70's used to have speedometers that maxed at 80mph... who knows how fast they could really go before something fell off or blew up, especially downhill. Somebody probably did, but they weren't telling.

The VC-25 may very well have a strengthened airframe; it is certainly meant to perform evasive maneuvers when necessary, so it wouldn't surprise me if it was able to fly faster than .92. Good luck getting anyone to tell you the official top speed, though.

I kind of doubt it can top mach 1 without damage, though; a lot of weird stuff happens to planes when they approach mach 1 if they're not designed for it.
 
StTim
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Re: True Max Speed Of 747/VC25

Sun Sep 11, 2016 6:37 am

Any plane designed purely for subsonic travel could only exceed Mach 1 in a dive. Jet engines cannot work with supersonic airflow entering the engines. Planes designed for supersonic speeds have aerodynamic devices in the inlet to slow the airflow to subsonic speeds.
 
BoeingGuy
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Re: True Max Speed Of 747/VC25

Sun Sep 11, 2016 6:52 am

flylku wrote:
I worked with someone who was a Flight Engineer on the VC25 during acceptance testing. He said they got it as slow as 95 knots and slightly above mach 1.

I was speaking to an FO on the 747-400 and he said once on a trip to NRT they had plenty of fuel and the only reason they could not do mach .95 is the FMS would not accept it. I think they were bored and only did this briefly.

I went to to business school with a former A-6 pilot and squandron commander who had a friend who was involved in flight tests on the 747 (he was stationed out at Whidbey Island so it would make sense that he might come in contact with Boeing pilots). He was told the 747 has no trouble exceeding mach 1.0. I think it voids the warranty though.

I think the big issue is control surface lock. The fusealage has a bit of a coke bottle shape and so in some ways conforms to the area rule.

If true, the 95 knot number is the one that is truly astounding.


I sense you are making stuff up. First of all, the FMS doesn't control everything the airplane does. There are other modes you can be in and manually push the thrust levels up. Also the bit about voiding the warranty sounds fake. Did any of those people actually tell you that stuff, or did you make something up?
 
b747400erf
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Re: True Max Speed Of 747/VC25

Sun Sep 11, 2016 9:35 am

RW01MIA wrote:
PacificBeach88 wrote:
To you 747 drivers out there, what is the true max speed of a 747? On wiki and other sources it lists it as mach .89. In this article about 9/11 Col. Tillman admits he was going mach .94 and the F16s were having a tough time catching up with Air Fore One that day without using afterburners. He also admits to being at FL45 which seems within spec. Any thoughts or comments?

http://www.politico.com/magazine/story/ ... sky-214230


A fair question but comparing apples to oranges somewhat. The VC25 is based largely on the 747 design, but is a very modified aircraft throughout. While you can compare its handling and performance specifications to a factory-build commercial 747, there are design and operational factors which impact the performance of the airframe. The ability to refuel midair allows the aircraft to fly slightly higher and faster than other 747's as the operating weight is substantially decreased.

You'll not be able to find accurate performance numbers for the aircraft. Anything online is pure conjecture and 747-200 specs are way off the mark. The actual performance characteristics of the airplane is classified. None of the a.net armchair aviators have a clue.

Good question.


The ability to refuel mid-air adds more weight as do all the communications and protection systems. The anti-missile and other countermeasures adds angles to the airplane fuselage design that would lower the speed also. That would translate into a lower operating ceiling and lower speed. It could partially be countered by a new wing and they do have more powerful engines but pushing the airplane to the limit is not done with the President on board. In an emergency they could push to the limits but so can the civilian 747-200. They have never risked mid-air refuelling with the President on board because of the risks.
 
RetiredWeasel
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Re: True Max Speed Of 747/VC25

Sun Sep 11, 2016 3:23 pm

b747400erf wrote:
In an emergency they could push to the limits but so can the civilian 747-200. They have never risked mid-air refuelling with the President on board because of the risks.


One of the more intelligent and accurate posts on this subject. Air Refueling AF 1 is a contingency plan with the POTUS on board. Although I'm sure the pilots maintain proficiency in the maneuver, to my knowledge it's never been done with him/her on board. Rendezvousing and flying 2 large aircraft within 20 feet of each other involves a certain degree of risk, one that I'm sure the National Command Authority don't want to take.
 
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flylku
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Re: True Max Speed Of 747/VC25

Sun Sep 11, 2016 5:31 pm

BoeingGuy wrote:
flylku wrote:
I worked with someone who was a Flight Engineer on the VC25 during acceptance testing. He said they got it as slow as 95 knots and slightly above mach 1.

I was speaking to an FO on the 747-400 and he said once on a trip to NRT they had plenty of fuel and the only reason they could not do mach .95 is the FMS would not accept it. I think they were bored and only did this briefly.

I went to to business school with a former A-6 pilot and squandron commander who had a friend who was involved in flight tests on the 747 (he was stationed out at Whidbey Island so it would make sense that he might come in contact with Boeing pilots). He was told the 747 has no trouble exceeding mach 1.0. I think it voids the warranty though.

I think the big issue is control surface lock. The fusealage has a bit of a coke bottle shape and so in some ways conforms to the area rule.

If true, the 95 knot number is the one that is truly astounding.


I sense you are making stuff up. First of all, the FMS doesn't control everything the airplane does. There are other modes you can be in and manually push the thrust levels up. Also the bit about voiding the warranty sounds fake. Did any of those people actually tell you that stuff, or did you make something up?


No, none of this is made up. The warranty bit was all in fun. The real question is not weather the VC25 can exceed Mach 1.0 (it certainly has the power to do so and by all accounts has) rather could it do so safely for an extended period of time. It sounds like this is only in the realm of test pilots.
 
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Stitch
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Re: True Max Speed Of 747/VC25

Sun Sep 11, 2016 5:53 pm

PacificBeach88 wrote:
...which makes me wonder if the VC25 pilots ever practice that on the VC25s or if they practice using the E4s instead? Or is that a simulator exercise only?


They practice on the E-4 fleet.


RetiredWeasel wrote:
b747400erf wrote:
In an emergency they could push to the limits but so can the civilian 747-200. They have never risked mid-air refuelling with the President on board because of the risks.


One of the more intelligent and accurate posts on this subject. Air Refueling AF 1 is a contingency plan with the POTUS on board. Although I'm sure the pilots maintain proficiency in the maneuver, to my knowledge it's never been done with him/her on board. Rendezvousing and flying 2 large aircraft within 20 feet of each other involves a certain degree of risk, one that I'm sure the National Command Authority don't want to take.


Correct.

The VC-25 was equipped with in-flight refueling as a contingency in case of a large-scale nuclear exchange that made it either impossible or too dangerous to recover on the ground and re-fuel. There is no reason to refuel the airframe in any other scenario.
 
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Spacepope
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Re: True Max Speed Of 747/VC25

Sun Sep 11, 2016 6:02 pm

RetiredWeasel wrote:
One of the more intelligent and accurate posts on this subject. Air Refueling AF 1 is a contingency plan with the POTUS on board. Although I'm sure the pilots maintain proficiency in the maneuver, to my knowledge it's never been done with him/her on board. Rendezvousing and flying 2 large aircraft within 20 feet of each other involves a certain degree of risk, one that I'm sure the National Command Authority don't want to take.


They did refuel with President Carter aboard an E-4.

b747400erf wrote:

The ability to refuel mid-air adds more weight as do all the communications and protection systems. The anti-missile and other countermeasures adds angles to the airplane fuselage design that would lower the speed also. That would translate into a lower operating ceiling and lower speed. It could partially be countered by a new wing and they do have more powerful engines but pushing the airplane to the limit is not done with the President on board. In an emergency they could push to the limits but so can the civilian 747-200. They have never risked mid-air refuelling with the President on board because of the risks.


Max altitude is not governed by the wing in this case, it can climb much higher than it's certified ceiling. The 748 has a newer cleaner wing and because of that it actually has a lower ceiling. The older draggier wing actually helped slow the plane down in an emergency descent.
 
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PacificBeach88
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Re: True Max Speed Of 747/VC25

Sun Sep 11, 2016 6:05 pm

Stitch wrote:
They practice on the E-4 fleet.


Thank you for that! :)
 
WIederling
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Re: True Max Speed Of 747/VC25

Sun Sep 11, 2016 8:41 pm

What is the usual TOW of AF1 ?
I don't think it will ever reach the base types MTOW, .. ?

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