A little bit of a pingpong...
Peter Stickney wrote in message ...
In article ,
(Bill McClain) writes:
snippage
Hi all,
My Joshua was saying, "See, I told you people can eject from
Blackbirds!" Hey, who knew?
Because its "ram-air" speed is quite low, around 350 KIAS due to the high
altitude & thin air. The major concern is oxygen supply-it is a looong way
down! The heat is irrelevant because the Blackbird heats due to
"heat-soaking".
Am I right about that Foxbat? It was going Mach 3+ because of runaway
engines? What happened to aircraft and pilot? I'd imagine the
engines would flame out and the pilot would punch out; I'd hate to
think that the Foxbat would just blow up or something.
NO runaway engines. Foxbat is THE first airplane with FADEC control RRD-15B
designed by Chekunov OKB. It is the aerodynamic movemens that have to be
monitored. At placarded speed of M 2.83 and 5.5g sustained turn at 30 tonnes
weight (MiG-25PD-P has 5 g limit), wingtips fold upward for 70cm each (due
to heavy wings-it has reservoirs INSIDE the wings, not "integrals"), even
with differential stabilators rolls are "bending" the wings!
I wouldn't say that it was runaway engines, myself. Pretty much all
turbojet/turbofan engines are limited by the strength of teh materiels
of the rotating components (Compressors & Turbines).
Correct. That's why Foxbat A engine turbines are covered with 30 micron
silver (0,03-0,05mm smoothnes) by electrolysis-5 kg per engine! Foxbat E
(MiG-25PD) uses silver/radium that gives 0,01 smoothnes on ?-15BD-300.
Remember that
these parts are highly loaded, and are spinning very fast, so there's
a lot of stress & strain on the blade roots and the disks that hold
the blades. The most common limit is the temperature of teh hot gas
entering the turbine section.
Correct for turbofans, wrong for the MiG low-pressure turbojets. The limit
for them is RAM-air pressure (i.e. compressor fans). Let me give You the
temperatures at max dynamic thrust; Engine inlet temperature 320C;
compressor max temp-700 Centigrade. Fuel-adding section temperature-300C
(fuel cooling!); Air-evaporation section with alcohol-87C. So, turbine gets
rather cool air/fuel/alcohol mixture. TET-1,000C. All at M2,8 at 11,000
meters (or 13,000 meters at Middle east). Estimated max speed flight time-40
minutes (it was only 8 minutes on first machines!)
Oh, heat soaking. Having built-in reservoirs rather than integrals like
SR-71 (that leak when airplane is "cold"!), evaporated air is bled from
AE-section at -20C to wings and fuselage compartments. For example, the
mighty 600-KW "Smerch" radar working temperature is 50-60C due to good
cooling, so there is no need for nitrogen-cooling. Same goes for wings and
fuselage, they are "air-blown".
That's pretty constant, though. 1500
Degrees K is 1500 Degress K no matter what altitude you're at, or how
fast you're going. The compreressor section, up front, is another
matter - As the engine's air is rammed into teh inlets and slowed
down, it's pressure and temperature increase. (This is, generally, a
good thing - the more air, at a higher pressure, the more thrust. As
teh air is compressed by each stage of the compressor, it heats up
more. At some point, it's possible to exceed teh tmperature limits of
the materiels in the compressor. Generally, the effects of an
overtemp in the compressor section aren't catastrophic, unless you're
above the limits for a long time. It will dramatically shorten the
useful life of those components, so an engine swap would be necessary
after landing to ensuer that the next flight's going to be safe.
It appears that that's what happened with the Foxbat over Egypt. The
pilot, for Tactical Reasons (Like getting his Recce Data back)
exceeded the placarded Mach 2.8 limit on the aircraft. He successfuly
landed the airplane in Egypt, and the engines got swapped.
Wrongo about Egypt. Pilot Bezevec (that's his name) went (dashed) to M3.2
due to Hawk SAM launch detection via RWR. No damage to the aircraft or
engines. The R-15B-300 engines on Bezevec's aircraft were installed after
General Kadomcev got killed in engine bay fire in April 1969 when engines
got placarded at lower temps. He was a test pilot and simple firewalled the
engines. Let me remind You that slightly-modified (I mean re-engined E-155)
MiG-25M can go M3.2 until it runs out of fuel.
However, the rest is fine. CIT and TIT limits MiG-25 to go over 1,200 Kmph
indicated airspeed at ANY altitude. That's why MiG-25 cannot break sound
barrier (without bpilot being reprimanded! 8-) at the sea level-compressor
becomes "overcompressed" at that level at 1,200 IAS/TAS and there is simply
too little air for afterburner to go over stage 1 safely without making
engine turbine running hot (afterburner has 3 stages/levels).
However, it has automatic stabilator-adjustment when firing R-40s to avoid
roll/yaw/pitch change (another first on the fighter). Stabilators are cut
like wings and stabilators on F-15 as a good anti-flutter measure (F-15
"stole" this feature from MiG-25, F-15 prototype had anti-flutter weights!),
efficient airbrake (also coupled with stabilator to avoid pitch change). A
low-level flying prototype of MiG-25P made a snap-up attack ripple-fire with
all four R-40(Radar and IR) and evaporated MiG-15 drone.
Lowest and slowest ejections are kind of interesting, too. I bet the
Navy probably holds some interesting records there, mostly at sea.
)
Not uncommon. Kadomcev killed himself since the darn aircraft continued to
fly. It was an outboard engine-bay fire so the plane probably just
disintegrated when exploded. When the darn thing, being that MiG-25, SR-71,
XB-70 or whatever starts to move, even clipped wings/stabilizers/engines
cannot make it stop to fly straight&level... the early (pre-production)
MiG-25s had smaller on early machines, and produced same interference like
on F-14 (hence the bigger "fishtails" on early 25-s) and even wigtips that
were good only for straight and level flight.
There have been some successful underwater ejections. Those are a lot
more dangerous than they may sound. Water's heavy, thick stuff.
Depending of the height, it is all the same if one drops at sea, lake or
concrete.
--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster-
Quite.
--
Nele
NULLA ROSA SINE SPINA