By: Sens
- 12th August 2008 at 22:00Permalink- Edited 1st January 1970 at 01:00
The Mig-25 Manual says nothing about PCB. Nor OKB MIG chief designer says anything about that.
See also Yefim Gordon-Mig-25. No trace of PCB.
The fact is that the Mig-25 has no any precompressor cooling.
Its engines use technology, which I mentioned earlier, that is not familiar in the west.
This problem was never solved in XB-70.
In fact, every a/c with mixed compression engines has this problem.
It was the Blackbird's J58 that often encountered unstarts, not the J93, but it had nothing to do with the engine and everything to do with the intake system. The unstarts were largely corrected with the addition of a computer control system to control the translating spike in the intake. Before that the spikes were controleld manually and failing to oeprate them within a very tight tolerance would lead to an unstart.
These are good wishes only.
Even SR-71 with digital intake controls, introduced in 1983, had this problems.
See SR-71 manual.
According to Manual, even with this digital system the problem persisted.
You can only imagine the magnitude of this problem before this.
It was surely awful.
By: firebar
- 13th August 2008 at 11:49Permalink- Edited 1st January 1970 at 01:00
I;m sorry but the article doesnt provide further explanation. What if the MiG-25R which was tracked flying over Israel at Mach 3.2 was indeed the one fitted with the R-15BF2-300 engines.;) Very good assuption, but do you have any proof for that, or is it just your personal opinion?.
Its engines were R-15B-300. Of course. In that time the R-15BF2 did not existed yet.
By: firebar
- 13th August 2008 at 12:13Permalink- Edited 1st January 1970 at 01:00
The enormous power of Mig-25 at high altitudes reveal this fact, from manual, of course. And that for the first version entered 1970:
-At 18 km altitude, its rate of climb, is 100 m/sec !!!
Compare this with service ceiling of 16 km for F-14A. Or 18 km for F-15A.
The difference is huge.
Or look at the speed:
-Mig-25: 2.83 M with 4 x big AA-6 or 4x 500 kg bombs.
-F-15C: 1.78 M with 4x Sidewinder
Bear in mind that the F-15 is the fastest and highest climbing american fighter.
Even Mig-23 has much higher speed:
-2.35 M with 2x big AA-24.
By: firebar
- 13th August 2008 at 12:26Permalink- Edited 1st January 1970 at 01:00
These are Mig-25 records which still stands:
-1967, speed over 1000 km closed circuit, with 2 tonnes payload, 2920 km/h.
-1967, speed over 500 km closed circuit, with 2t payload, 2982 km/h.
-1973, speed over 100 km closed circuit, no payload, 2605 km/h.
-1973, max altitude, with 2 t payload, 35230 m.
-1973, max altitude, no payload, 36240 m.
These are achieved with standard engines R-15B-300.
In 1977 it achieved even more with R-15BF2 engines:
-Max altitude , with 2 t payload, 37080 m.
-Max altitude , no payload, 37650 m.
There are also time to climb records which still stands.
Which other a/c can boast with such array of records?
By: Sens
- 13th August 2008 at 12:37Permalink- Edited 1st January 1970 at 01:00
These are Mig-25 records which still stands:
-1967, speed over 1000 km closed circuit, with 2 tonnes payload, 2920 km/h.
-1967, speed over 500 km closed circuit, with 2t payload, 2982 km/h.
-1973, speed over 100 km closed circuit, no payload, 2605 km/h.
-1973, max altitude, with 2 t payload, 35230 m.
-1973, max altitude, no payload, 36240 m.
These are achieved with standard engines R-15B-300.
In 1977 it achieved even more with R-15BF2 engines:
-Max altitude , with 2 t payload, 37080 m.
-Max altitude , no payload, 37650 m.
There are also time to climb records which still stands.
Which other a/c can boast with such array of records?
For the benefit of the others. Such records were not flown by standard engines and aircraft. Just listed for the FAI. Only the related time, height, speed and the allowed weight for the class is recorded. ;)
By: mike currill
- 13th August 2008 at 12:58Permalink- Edited 1st January 1970 at 01:00
One thing it is worth remembering is that it is unwise to underestimate the capability of your oponent in any combat situation, that is a sure way to end up being slapped down very hard regardless of whether it is land, sea or air combat you're talking about.
Another thing is that it is all very well having these wonderful high speed machines until it comes to a turning fight. Speed bleeds off from supersonic to high subsonic very quickly in a turning fight and then the guy with the best turning circle has the advantage.
Far more troubling, however, were problems in the new, automatic AICS system, which would inexplicably recycle during supersonic flight, causing an "unstart," where the shockwave from the forward fuselage, rather than being deflected past the inlet and under the wing, instead fell directly into the inlet. Not only did this change in inlet airflow cause a brief flameout on the engines, but it also caused a sharp roll in the direction of the GOOD engine set. For pilots, this is fairly odd behavior caused by the shape of the XB-70's wing, combined with the lowered tips (and on Ship One, accentuated by the lack of dihedral), which as the aircraft yawed to the "dead" side, caused a roll away into the "good" side. So, during an unstart (described by Fitz Fulton as "being T-boned by a locomotive and thrown off a cliff"), the pilot would have to apply rudder into the direction of the roll, which is a bit unnatural.
The problem was the new Automatic Inlet Control System (AICS) introduced on AV2, not the J93 engine. The AICS had a weird habit early on of recycling and resetting its position in midflight, causing an unstart. Not fun at all, but not a fault of the engine either as you keep claiming.
The problem was the new Automatic Inlet Control System (AICS) introduced on AV2, not the J93 engine. The AICS had a weird habit early on of recycling and resetting its position in midflight, causing an unstart. Not fun at all, but not a fault of the engine either as you keep claiming.
Lot's of planes had the unstart problem including the XB-70, the Blackbirds, F-4 Phantom, and Crusader III. In none of them was it the engine's fault and in all of them they eventually got the problem resolved.
By: firebar
- 14th August 2008 at 10:55Permalink- Edited 1st January 1970 at 01:00
Lot's of planes had the unstart problem including the XB-70, the Blackbirds, F-4 Phantom, and Crusader III. In none of them was it the engine's fault and in all of them they eventually got the problem resolved.
First of all, the F-4 and F-8 had no mixed compression engines and, so, they had no experiences with unstarts.
The F-4 and F-8 had ordinary external compression engines, where normal shock wave never entered inlet duct, so there was no unstarts.
On the other hand, the mixed compression engine experience unstarts by its nature. It can not be avoided. Only its magnitude can be reduced to lower level.
See SR-71 Manual: Even with DAFICS digital inlet control, the unstarts are frequent.
The slightest air density change can trigger unstarts. it is very sensitive.
Because of that only two a/c used mixed compression. The Blackbird and XB-70.
By: SOC
- 14th August 2008 at 13:23Permalink- Edited 1st January 1970 at 01:00
If the MiG-25 was a "multi-mode" aircraft, you'd be able ot use the same jet for both intercept and reconnaissance. You can't. Just like the Blackbird, different variants existed for different missions.
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By: Sens - 12th August 2008 at 22:00 Permalink - Edited 1st January 1970 at 01:00
For the benefit of the others.
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By: sferrin - 12th August 2008 at 22:48 Permalink - Edited 1st January 1970 at 01:00
I'd read the Mig that hit 123k used it but I didn't know it was standard issue. Kindof a kludge for the envelope the Mig typically flies IMO.
Posts: 1,189
By: martinez - 12th August 2008 at 23:18 Permalink - Edited 1st January 1970 at 01:00
...not a standard flight, it hit the altitude 37650m only once, what is 123523.6ft.
http://records.fai.org/general_aviation/history.asp?id1=21&id2=1&id3=4
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By: sferrin - 12th August 2008 at 23:21 Permalink - Edited 1st January 1970 at 01:00
Where did I say the 123k flight was a standard flight?
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By: martinez - 12th August 2008 at 23:45 Permalink - Edited 1st January 1970 at 01:00
sorry, just stating the facts...
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By: firebar - 13th August 2008 at 11:42 Permalink - Edited 1st January 1970 at 01:00
You did not read anything about XB-70 unstarts? Its odd because there are many sources. Here is one:
http://www.transterrestrial.com/archives/2008/02/a_kludge_1.html
This problem was never solved in XB-70.
In fact, every a/c with mixed compression engines has this problem.
These are good wishes only.
Even SR-71 with digital intake controls, introduced in 1983, had this problems.
See SR-71 manual.
According to Manual, even with this digital system the problem persisted.
You can only imagine the magnitude of this problem before this.
It was surely awful.
Posts: 875
By: firebar - 13th August 2008 at 11:49 Permalink - Edited 1st January 1970 at 01:00
Its engines were R-15B-300. Of course. In that time the R-15BF2 did not existed yet.
Posts: 875
By: firebar - 13th August 2008 at 11:58 Permalink - Edited 1st January 1970 at 01:00
Do you know what the Mig-25 inlet picture reveal?
Posts: 875
By: firebar - 13th August 2008 at 12:13 Permalink - Edited 1st January 1970 at 01:00
The enormous power of Mig-25 at high altitudes reveal this fact, from manual, of course. And that for the first version entered 1970:
-At 18 km altitude, its rate of climb, is 100 m/sec !!!
Compare this with service ceiling of 16 km for F-14A. Or 18 km for F-15A.
The difference is huge.
Or look at the speed:
-Mig-25: 2.83 M with 4 x big AA-6 or 4x 500 kg bombs.
-F-15C: 1.78 M with 4x Sidewinder
Bear in mind that the F-15 is the fastest and highest climbing american fighter.
Even Mig-23 has much higher speed:
-2.35 M with 2x big AA-24.
Posts: 875
By: firebar - 13th August 2008 at 12:26 Permalink - Edited 1st January 1970 at 01:00
These are Mig-25 records which still stands:
-1967, speed over 1000 km closed circuit, with 2 tonnes payload, 2920 km/h.
-1967, speed over 500 km closed circuit, with 2t payload, 2982 km/h.
-1973, speed over 100 km closed circuit, no payload, 2605 km/h.
-1973, max altitude, with 2 t payload, 35230 m.
-1973, max altitude, no payload, 36240 m.
These are achieved with standard engines R-15B-300.
In 1977 it achieved even more with R-15BF2 engines:
-Max altitude , with 2 t payload, 37080 m.
-Max altitude , no payload, 37650 m.
There are also time to climb records which still stands.
Which other a/c can boast with such array of records?
Posts: 875
By: firebar - 13th August 2008 at 12:31 Permalink - Edited 1st January 1970 at 01:00
Comparing to the above mentioned Mig-25 records:
YF-12:
-1965, closed circuit over 1000 km, with 2 t payload, 2718 km/h.
-1965, closed circuit over 500 km, with, 2 t payload, 2644 km/h.
Note that it is far below that of Mig-25 achieved.
Posts: 11,742
By: Sens - 13th August 2008 at 12:37 Permalink - Edited 1st January 1970 at 01:00
For the benefit of the others. Such records were not flown by standard engines and aircraft. Just listed for the FAI. Only the related time, height, speed and the allowed weight for the class is recorded. ;)
Posts: 8,505
By: mike currill - 13th August 2008 at 12:58 Permalink - Edited 1st January 1970 at 01:00
One thing it is worth remembering is that it is unwise to underestimate the capability of your oponent in any combat situation, that is a sure way to end up being slapped down very hard regardless of whether it is land, sea or air combat you're talking about.
Another thing is that it is all very well having these wonderful high speed machines until it comes to a turning fight. Speed bleeds off from supersonic to high subsonic very quickly in a turning fight and then the guy with the best turning circle has the advantage.
Posts: 12,009
By: SOC - 13th August 2008 at 13:22 Permalink - Edited 1st January 1970 at 01:00
You're using a comment somebody left on a website as your factual basis for that argument? Are you serious?
Try this:
http://www.labiker.org/xb70.html
The problem was the new Automatic Inlet Control System (AICS) introduced on AV2, not the J93 engine. The AICS had a weird habit early on of recycling and resetting its position in midflight, causing an unstart. Not fun at all, but not a fault of the engine either as you keep claiming.
Posts: 9,683
By: sferrin - 13th August 2008 at 15:21 Permalink - Edited 1st January 1970 at 01:00
Don't forget, that's at 123,000 feet while pulling 11Gs. :diablo: :cool::cool:;);)
Posts: 9,683
By: sferrin - 13th August 2008 at 15:23 Permalink - Edited 1st January 1970 at 01:00
Lot's of planes had the unstart problem including the XB-70, the Blackbirds, F-4 Phantom, and Crusader III. In none of them was it the engine's fault and in all of them they eventually got the problem resolved.
Posts: 875
By: firebar - 14th August 2008 at 10:55 Permalink - Edited 1st January 1970 at 01:00
First of all, the F-4 and F-8 had no mixed compression engines and, so, they had no experiences with unstarts.
The F-4 and F-8 had ordinary external compression engines, where normal shock wave never entered inlet duct, so there was no unstarts.
On the other hand, the mixed compression engine experience unstarts by its nature. It can not be avoided. Only its magnitude can be reduced to lower level.
See SR-71 Manual: Even with DAFICS digital inlet control, the unstarts are frequent.
The slightest air density change can trigger unstarts. it is very sensitive.
Because of that only two a/c used mixed compression. The Blackbird and XB-70.
Posts: 875
By: firebar - 14th August 2008 at 11:21 Permalink - Edited 1st January 1970 at 01:00
How many a/c types can climb to 123.000 ft ?
How many Mach 3 types can endure 11G without breaking apart ?
Comparing to multi mode Mig-25, the Blackbird is mere fragile fuel tank, with max allowed g loading like ordinary airliners.
The Mig-25 is limited to 5 G at 2.5 Mach at 30 t weight.
www.sergib.agava.ru/russia/mikoyan/mig-25/records
It is the highest G limit by any figher, even today, at speeds over 2 Mach.
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By: SOC - 14th August 2008 at 13:23 Permalink - Edited 1st January 1970 at 01:00
If the MiG-25 was a "multi-mode" aircraft, you'd be able ot use the same jet for both intercept and reconnaissance. You can't. Just like the Blackbird, different variants existed for different missions.
Posts: 9,683
By: sferrin - 14th August 2008 at 14:17 Permalink - Edited 1st January 1970 at 01:00
You obviously know nothing about it. They both had problems as anybody who's made a passing glance at the history of either aircraft knows. :rolleyes: