MiG-25M (Ye-266M) Development
The 1972 directive ordering the service entry of
the MiG-25RB, ‘RBK and ‘RBS also elaborated
on the upgrade possibilities of the basic design.
The military wanted an increase in range
at low and medium altitude and an increase in
ceiling and maximum speed.
The Mach 2.83 speed limit imposed on the
MiG-25 was purely theoretical, since the aircraft
had the potential to go faster from the very start.
High speeds reduced lateral stability and service
life, but there were cases of pilots exceeding
the speed limit without harming the aircraft.
Therefore, the designers intended to reach a
Mach 3.0-3.2 top speed so that the MiG-25
could outperform its arch-rival, the SR-71A –
the world’s fastest recce aircraft. This could be
achieved by fitting the MiG-25 with more powerful
and fuel-efficient engines.
As far back as the early 1960s, a group of
engine designers led by Shukhov and Rotmistrov
proposed a comprehensive upgrade of
the R15B-300 turbojet. The idea materialised as
the uprated R15BF2-300, Izdelye 65M. The
improvement in performance was achieved by
adding a compressor stage and increasing the
combustion chamber and turbine temperatures.
As compared with the R15B-300, the
R15BF2-300 had a lower specific fuel consumption,
a higher thrust (10,000kgp/22,045lb
st dry and 13,230 to 14,500kgp/29,166 to
31,966lb st reheat) and a higher compressor
pressure ratio (4.95 vs 4.75).
The two engines were perfectly interchangeable,
having identical dimensions and mount-
ings. Providing the airframe was made more
heat-resistant (that is, because of the higher
turbine temperature), the new engines offered
a substantial increase in rate of climb, ceiling,
range and speed (up to 3,500km/h, or
2,187mph).
The Mikoyan OKB started a massive research
effort with a view to increasing the MiG-25’s top
speed, concentrating mainly on aerodynamic
stability and airframe/engine thermal limits. The
aircraft’s principal structure was made of steel
and thus was heat-resistant enough. Some
parts of the airframe, however, such as the
radome and forward fuselage, wingtips, flaps
and ailerons, were made of Duralumin and
plastics. They were not subjected to significant
structural loads but experienced high temperatures
and had to be replaced with steel or titanium
honeycomb structures. This, in turn, called
for new technologies, Therefore the Mikoyan
OKB suggested to split the work into two
stages, ie, test and refine the engine on a structurally
standard MiG-25 first and come back to
the speed issue later.
Both the WS and the Ministry of Aircraft
Industry went along with this approach and
gave the go-ahead for Stage 1. In September
1964 the Ministry issued a directive detailing
the test programme of the re-engined MiG-25.
Yet the theoretical part, manufacturing and
bench testing of the R15BF2-300 took longer
than predicted, and flight tests did not begin
until 1973. The VVS initially allotted a single
MiG-25 for test purposes, which was later
joined by a second aircraft.
Aircraft No.1 was a MiG-25RB which was
given a new factory number (f/n) 02-601, after
being modified (hence the tactical number
Blue 601′). Aircraft No.2 was a standard MiG-
25PD built in 1973 (f/n 84019175) which made
its first flight with standard engines on 12th
June 1973 with Ostapenko at the controls.
Later it was flown by Fedotov, Fastovets, Orlov
and others.) On 30th August 1973 the aircraft
received its intended R15BF2-300 engines,
new c/n (841710) and the tactical number ‘Blue
710′.
From then on, the two aircraft served as testbeds
for the new turbojet with the provisional
designation MiG-25M (Modifitseerovannyy –
modified). The conversion work was completed
very quickly but refining the engine took a
considerable time. Still, it was worth the sweat:
the engine did produce the claimed performance.
The service ceiling exceeded 24,200m
(79,396ft) and supersonic cruise range was
1,920km (1,200 miles) in clean condition or
2,530km (1,581 miles) with a 5,300 litre (1,177
Imp gallon) drop tank.
The re-engined MiG-25 never entered production
– for several reasons. First was the test
programmes of two new aircraft, the MiG-25
Izdelye 99 and the MiG-31, which also began in
1975. Both aircraft were powered by the
Solov’yov PS-30F (D-30F) engine with a similar
rating but a lower specific fuel consumption
(SFC). Second, the aero engine factories were
tied up with other orders and could not produce
the R15BF2-300. Finally, the PVO top command
was more interested in the MiG-31 than
in an upgrade of the existing MiG-25. Therefore,
the MiG-25 programme was terminated.

MiG-25 with Solov’yov PS-30F engines
(Izdelye 99)

The production MiG-25P interceptor fulfilled all
design requirements except range. To increase
range one MiG-25P was experimentally reengined
with Solovyov PS-30F afterburning turbofans
rated at 15,500kgp (34,170lb st). Also
known as the D-30F, this engine was a derivative
of the ‘pure’ D-30, rated at 6,800kgp
(14,991lb st) which powered the Tupolev Tu-
134 ‘Crusty’ airliner, not the much later and
much larger D-30KU/D-30KP, which is a totally
different engine. The test-bed was designated
Izdelye 99 and appropriately coded ‘Blue 991’.
Later, a MiG-25R was similarly converted and
coded’Blue992′.
Unlike the MiG-25M described above the
new engines required major modifications to
the airframe. Still, outwardly the aircraft was little
different from standard MiG-25s and the
internal fuel volume remained unchanged
(19,700 litres/4,377 Imp gallons). The new turbofan
was expected to improve rate of climb
and especially range (particularly at subsonic
speed) by virtue of a lower SFC. Besides, the
same engine was selected to power the future
MiG-31.
A short while earlier, two MiG-25M test-beds
powered by Tumansky R15BF2-300 turbojets
had been evaluated, but there was no knowing
if and when this engine would enter production.
The new and fairly complex MiG-31 fighter
weapons system could also take a long time
testing. Thus, a MiG-25 fitted with the new fuelefficient
engines could supplant the standard
MiG-25PD on the Gorkii production line for a
while until the MiG-31 would be ready.
The scope of the Izdelye 99 programme was
much larger than with the MiG-25M. However,
with assistance from the Gorkii aircraft factory
and due largely to the insistence of lead engineer
M Proshin the technical problems were
solved quickly enough. Shortly after test flights
commenced a subsonic cruise range of
3,000km (1,875 miles) without drop tanks was
achieved. Supersonic flight, though, caused
more problems.
Normal take-off weight during tests was
37,750kg (83,223lbs), including 15,270kg
(33,664lb) of internal fuel; MTOW with drop
tank was 42,520kg (93,738lb). Range was
increased to 2,135km (1,334 miles) in supersonic
cruise or 3,310km (2,068 miles) at transonic
speed, and service ceiling was boosted
to 21,900m (71,850ft).
However, the MiG-31 was designed around
the D-30F engine from the outset. And when
the MiG-25MP, as the first prototype MiG-31
was initially designated, entered flight test in
the autumn of 1975, interest in the MiG-25/D-
30F re-engining project waned. In fact, no one
took the trouble to study the aircraft’s performance
completely. The two modified aircraft
were relegated to the role of engine test-beds
under the MiG-31 development programme.

MiG-25PA(Ye-155PA) Interceptor
In the mid-1960s the Mikoyan OKB was working
on an interceptor project referred to as the
Ye-155PA. This aircraft was to be capable of
destroying targets flying anywhere between
100 and 30,000m (328 – 98,425 ft) at speeds of
3,500 to 4,000km/h (2,187 – 2,500 mph). To this
end, it was to be equipped with the brand-new
‘Smerch-100’ radar, later renamed ‘Zaslon’
(Shield), and armed with the equally new R-100
missiles. The powerplant consisted of two
R15BV-300 turbojets with an improved high
altitude performance (Vysotnyy – high altitude)
which would take the aircraft to Mach 3.5.
Later, the requirements changed, especially
regarding speed, and the project was discontinued.

Well, judging by this projects, the soviets had the choice of increasing the MiGs top speed , and even prolonging supersonic flight, but they choosed not to. So, I guees they were pleased with what they had.

well….I’m not living in Serbia, so I really don’t care, since I don’t pay taxes I’m not to decide.
But I don’t think there will be a true need for a 40 million$ jet fighters in the foreseeable future.
From my standpoint, you’re rather lucky having a decent number of G-4 airframes. With some modifications and upgrades, and in somewhat larger numbers, they should be able to meet any future needs. And frankly, there’s still some room for improvement on the J-22. More powerful engines, for example, and you could have a supersonic jet(offcourse, with extra aerodynamical modifications).

Croatian Hinds

How bout Nikola Tesla’s beams of death 😀 ?

Its been said that he came up with a design of a weapon capable of destroying entire squadrons flying in the air, aswell as balistic rockets, stealth or no stealth. It was in his late years, when he was quite poor, so he decided to offer his design for sale. It is rumoured that he offered it to Yugoslavia, for 500 dinars(cheeaaap 🙂 ), but they turned him down, beliveing that he became crazy. I wonder what has become of his manuscripts that were taken by the FBI the very day he died….

back on the subject? What kind of a effect would have if they would detonate a nuclear device in a suborbital trajectory, wright above the planes?

For Croatia

– sell, burn or sink the entire fleet of MiGs-21.
– buy some 15-20 helicopters for SAR and other navy/police/coast-guard/firedept missions
– do NOT buy used F-16s from Belgium or any other.
– invest the money that would be spent for purchasing F-16s to a UAV project(which was operational during the war. I can’t find a single picture on the internet)
– burn or give away three missile gunboats that are currently in service.
– build coast-guard boats.
– enhance coastal ssm-s and sam-s
– decommision the sub
– buy and build the Degman
– professional army of some 20 000- 25 000 units(btw, this is what is going to happen in a year or two, but anyway…)
– buy more Canadairs for fire dept.(this maybe isn’t a army issue, but still)

there were excelent threads posted on the navy forum, too bad they are all gone. I wish that webmaster reconsiders his decision.

BTW, does anyone know any good WW1 & WW2 navy forums?