SchorschMay or may not! A lot of guessing against a given statement!
What the heck are you all complaining about?
Getting an aircraft’s top speed requires very detailed knowledge of many factors and the atmospheric conditions of that very day. If one actually tries it I would laugh on him.
We don’t even know the Raptors exact thrust rating at sea level static.
As for the mention of the Mirage IV, did this aircraft have supersonic cruise capability as good as the B-58? Or was it more like the f-111 in that it could go fast, but not for very long periods?
Surely, the B-58 couldn’t “supercruise”, and Mirage IV couldn’t do either. So, both at the same level of “supercruise”.
Why was the B-58 abandoned so quickly? IIRC, its career was not too long.
Nice aircraft without a real mission.
Also, it tended to crash frequently.
And its electronics were due for extreme make-over in the early 1970ies.
The options were: substantial investment or desert airstrip.
Loaded up it was more like 80 tons. Not sure where the 45 ton figure comes from …
The B-58 (like the SR-71 or XB-70) had max take-off and max flying weight. Taking of at “max flying weight” the B-58 would have required an 8 mile runway and tires able to make 550mph.
Tu-144 could, it was the Russian SST.
Initially it couldn’t, which was one of the biggest issues.
Rated at it maximum output (without looking at self-destructing the engine) you’re looking at a few hours at 110 kN.
Note that it was only matter of MATERIALS and SIMPLE set of modification (in priciple) to make it FULLY M 3.0 capable and that it was realisticaly and succesfuly bench-tested at M 2.5. SO = Demonstrated REAL M 2.5 capabilties.
With such a reduction of engine life-span and airframe fatigue i dont see that point unless you can afford bining both after only as few hundred hours including repairs.
That is also a good indication how the MiG-25 got its Mach3-potential. Turbojets – and afterburning turbofans generally, too – could achieve quite good top speeds, as engine thrust increased with Mach number (given correct inlet system).
SchorschTrue enough. My bad – they were including alt landing site fuel loads plus below mach level climb out over population centers and landing circuit speeds. Those numbers came straight out of the book, (page 152). There was also a skin temp limit (avg) of 620F that they would take into consideration. They never ran the XB-70 for the est 2.5 hours continuously, although the 30 mins at mach 3 speed the engineers felt was as hot as the airframe was going to get – so they felt confident that it could achieve the mach three speed until the minimums (fuel) were reached. It’s interesting to note that they have a picture of the mock up with an air re-fueling probe door yet the two flight articles did not have them installed – which makes sense for a test/research aircraft. We can assume that had it gone into service it would have had these installed. For an aircraft that used either JP4 or JP6 and was limited by skin heating and heat soak through to the fuel tanks – the authors have no answer for why the program did not use the JP7 fuel that the Blackbirds used successfully. I can only guess that it was a cost factor (4X as much) which makes sense since the program was always short of money after FY64.
The fuel was potentially a cost issue. Aside from that the number of aircraft in service would have required new infrastructure. Different than the SR-71/A-12 the B-70 was supposed to be a line aircraft, not a fancy CIA spy plane making on average a quarter flight hour per week.
The mission profile was probably a subsonic cruise to 2000km ahead of target, top up by tanker, then a M3 dash in&out and another rendezvous with the tanker. A mission from USA to Russia and back on internal fuel with Mach3-section was never considered, no aircraft in the US inventory could do that before the B-52H.
Conventional bombs are indeed a stupid idea. And I guess this killed the B-70. All single-mission (nuclear delivery) aircraft in USAF/USN inventory had a short service life, see also B-58, A-5, which had similar issues (performance=great, usefulness=poor).
Different kinds of engines and different kinds of fuel tanks.
The engines normally don’t mind, at least not at speed&altitude.
Why on earth would you do that? Use the KE to send them a long way and hit hard. The YF-12 released weapons from an internal bay at Mach 3. There’s no reason the XB-70 wouldn’t have been able to Why do you think they did the bay doors the way they did?
The problem is that a 500lbs bomb dropped from 70000ft and Mach 3 might hit anywhere within a a five mile radius. Precision guided ammunition wasn’t available back then, so the only reasonable payload was nuclear.
They over estimated the risk from SAMs as well as the utility of ICBMs. They thought the day of the manned bomber was over.
As successfully proved in 1972, the vintage B-52 could fight down an air defense with acceptable loss ratio, and overall at a fraction of cost of supersonic bombers. The supersonic bomber does not improve its survivability the same pace as the cost per dropped bomb increases.
If the story becomes nuclear, it doesn’t matter any more.
The time of the “manned bomber” for the purpose of nuclear first strike was indeed over, as the cost-benefit ratio was sick. From the early/mid 60ies it was all about deterrence, and nobody actually wanted to strike anyone.
An ICBM costs less than half the price of a single bomber, delivers more weapons in one run (although it only has one), it requires a fraction of the personal, is basically undefeatable after launch and very hard to kill before.
SchorschYou don’t know what the top speed of the F-35 is. Mach 1.6 is the KPP THRESHOLD! Not a Mach limit.
Correct, it hasn’t demonstrated it yet, so we have to go with the pathetic M1.2 or has it has demonstrated so far.
If we were very eager, we wouldn’t even call it supersonic at all before an operational version with a MMO printed in its flight manual becomes available. However, as I trust LockMart, I guess they gonna make over the sound barrier.
SchorschPehaps well but also includes non-standard use of the definition of the USAF word cruising itself, leading to think that these figures are rather lower than higher than the ones you provides with standard use of throttle settings.
This of course ALSO applies to other non-US aircraft supercruising.
I use 100% throttle for military power.
Problem is: I am scaling the engine with reference thrust, and as you know, the actual thrust largely depends on the engines software limitations, which easily may change thrust by +/- 10% (for lifetime considerations for example).
A record like achieving M1.72 was most likely done using full engine rating, which may not be available to line F-22 in peacetime, and which may not be part of the official flight envelope.
Changing atmospheric conditions are completely blanked out, so no hot days or winds.
There are many many small details that can change the corner values, but overall the metrics remain similar. If I close into the F-22 (supposed) specific range to 10 or 20% for a variety of Mach numbers, we can call the result satisfactory for educational (= understanding “supercruise”) purposes.
SchorschIt is the original requirement that JASDF set for the FS-X project (more than 450 NM / 833 km combat radius for anti-ship mission) in 1980s, not necessarily to be the real performance of the F-2A/B today.
I guess if it was requirement, it was achieved, at least somehow (given the atmospheric conditions many details may change).
The configuration with 4 AShMs is quite draggy, so that a2a radius is much more.
An important difference between EF and F-2 is the relative size (EF has more than 20% more wing area) and the payload accommodation. With given load the F-16 based F-2 will have a very ugly initial fuel flow.
SchorschConcerning the Specific Range of the F-22, it is actually fairly simple to arrive at the values Stevenson used, and although they don’t have backing from any official source, they are somehow useful, as long as Lockheed Martin has not re-defined the physics of supersonic flight, which I honestly doubt.
So, take a contemporary fighter, plug in weight and engine data, assume 10% better SFC, 10% less drag, etc. And there you go! This aircraft makes it to M1.6 in supercruise, which is a bit short of the often quoted M1.72, but for a guess-approach fairly accurate. You cannot get peak values from such approaches, only relative values.
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Compare to:
http://forum.keypublishing.co.uk/showpost.php?p=1344565&postcount=27
sferrin may in the mean time wait until the F-22 manual is released to the public, which I would expect in 2030 earliest.
SchorschMiG-29 & Su-27 both have mudguards and retractable FOD screens in the intakes – the Su-27 has strong downlock that keep the maingear rigidly attached to the fuselage sides for added strength – even the new Yak-130 trainer has a blanked-off intakes – but they are designed to operate in austere environments or dirty Russian airstrips, not ploughed fields.
There has been some recent footage of Su-27’s taking off and landing on dirt strips/peri tracks – so it could be argued that Russia’s frontline fighter is capable of ‘rough field’ operation – it depends on your definition
Agreed on this. It is always the question which level of attrition was considered acceptable. Also, which performance limitations were imposed (reduced take-off weight, dry power take-offs).
Maybe the increased FOD resistance is to some degree due to lower quality airfields.
We see on many occasions that Russian equipment accepts tougher treatment by its operators.
Very interesting in this context: people remember the briefing shown on YouTube about the Indian Flankers. The guy there stressed that their aircraft had a specific problem with FOD. Maybe that play a role, too, while I have problems to think that Russian engines are more prone to FOD damage and therefore need more protection airframe-wise.
SchorschIn the engine dpt, the maximum thrust is Opitimised for SEA level (STVOL Operation) and inlets are ALSO oprimised for maximum output at sea-level so the whole aircraft is de-facto optimised for low-altitude/high-transonic flight regimes.
The F-35B is the STOVL aircraft, it will have corresponding inlets. The “A” will be optimized for cruise flight at altitude and high subsonic speeds, and will have secondary design point at Mach 1.5. Pretty much like F-16 and F-18.
The crappy top speed of M1.6 besides being clean and having quite a lot of thrust indicates a poor propulsion system performance beyond M1.5 and a high level of drag.
SchorschWhat sometimes gets lost in this “Hail the F-22” presentations is that supercruise still is limited to a short time and moderate distance.
So the “employ speed” is somehow misleading. Most of the time both aircraft operate at M.85, and the F-22 can have a longer supersonic leg with less combat radius penalty.
Orienting on the values from a few pages before, assuming .07/.035 nm/lbs specific range for subsonic/supersonic operations, 100nm of supersonic translate into 200nm at subsonic, while for an F-35 this would be more like 60 to 200.
Sure a big advantage, but also brings disadvantages (like most features on a stealth aircraft have their opposing downs).
SchorschDo not forget the MiG-23 and MiG-27 ‘Flogger’ series!
One thing that the Russians/Soviets have never forgoten about WWII is the vulnrability of fixed runway!Saab Viggen
AMX?
Su-17/22 ‘Fitter’
Su-25 ‘Frogfoot’
Regards
Pioneer
What do you need for “rough field”:
– low pressure tires (means big wheel on small aircraft)
– FOD-insensitive engine intake
– rugged shock absorbers
Then you can have short take-off capability, where you need
– lots of thrust
– good lift coefficients
– slats and flaps
– low take-off and approach speeds
If you have the one, you don’t need the other. I don’t believe one can operate any jet from unprepared strips. And neither from classic dirt strips (apart the implications by weather in middle Europe). Possible is an operation from short sections of road or damaged airports which still afford to have some intact taxi ways.
So a MiG-23 does not necessarily have “rough field” capability, like the Tornado it doesn’t need as it can take-off easier than other aircraft.
Aircraft with good radius do not need that capability, either. An F-15 or A-10 can normally be operated from farer behind the front. The A-10 additionally can cope with short runways.
SchorschEngine thrust, CD, engine cycle, aircraft weight, intake efficiency, etc. The public doesn’t have those numbers for the F-35.
So you relying entirely on the stuff that comes out of the USAF press department.
I am sorry for you, but that will severely hamper your ability to get behind the figures. Nobody claims a single digit percentage accuracy, but aircraft of 2008 follow same rules as that of 1970, and engines are prone to similar limits.
SchorschNot all of it but some very good indications still.
And one can take an existing design and do some dead reckoning from that.
Not good enough to give single percentage accuracy, but good enough to help one understand how it works.
I am using the F-16 or MiG-29 (or F-4, F-106, MiG-23) as basis and then plug in weights and dimensions and using “better than” factors. Actually, I came quite good in the ballpark of many aircraft with that method, at least of those I have detailed performance manuals about.
SchorschIf LM can reduce weight in its preproduction series, why can’t KNAAPO do the same?
Actually LM hunts its empty weight target ever since. They are not there yet.
Also we saw a jump in the F-22s empty weight by quite a few kilos.
There is no disrespect, just the collective memory.
A decrease in empty weight coupled with an increase in thrust, internal fuel and capability seems questionable. Or the original Suchoi 27 was designed crappy, which I really don’t think.
All this “composites” do less magic than one might expect, besides the original Suchoi 27 was already on the edge of technology, using titanium and stuff.
SchorschI guess if its a Fantasy Air Force, I’ll have a few squadrons of these…
Airfield compatibility might be an issue.
SchorschThen a typical F-16 drag polar…
I may count some beans and say that a “drag polar” is normally lift as function of drag, not zero lift over Mach number.
But aside bean counting, there is basically one useful data set for a 4th generation fighter out there, the MiG-29″A” from an aerodynamic manual.
Now, the data presented there has its shortcomings (especially everything is written in Russian, you have to guess yourself through it), but it is the best stuff you can find in the open internet. Especially does it have drag (including some external stores) & installed thrust data, along with many derived performance figures. So you can actually validate your stuff to some extent.
Now, taking it for the present example, we take an a2a configured MiG-29 with 2 SR-AAM and 2 MR-AAM, full internal fuel (appr. 15.2t gross weight) with the standard dry thrust of ~4900daN (per engine). Results are compared to the performance given within the manual and show good correlation.
Upper left: lift over drag
Upper right: fuel flow (includes throttle influence on SFC)
Lower left: specific range
Lower right: specific excess power
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As we can see, we have a peak SEP of 85 m/s, and some marginally positive values above M1.0, but they soon diminish (negative SEP means you cannot maintain level flight).
Supercruise means that you have substantially positive (~ at least 10 m/s) SEP through supersonic region.
Now, we increase thrust by 20% (that is a pretty tough increase!). Leaving everything else constant.
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The thrust increase pushes our SEP close to 120 m/s, basically linear with the thrust increase. But on the very right side we see a marginal increase, but no line really touches M1.2.
See the decrease in specific range and increase in fuel flow, although aerodynamics and weights are unchanged!
Conclusion: you can’t make it supercruise with just more thrust.
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