adriannIt is not easy, nobody wants to expose its flaws
adriannThere is a thread “Maxium speed Questions” on this forum, interesting because one can not find answer to this issue in any book, yet it is very simple.
adriannWhat are you looking for? You want handy stuff, put it on the table, and say “airplane A is better than airplane B”. Honestly, that’s bullcrap (especially 3rd generation aircraft have a theoretical maximum lift, which is unaccessible due to controllability issues at high AoA).
Maximum lift is interesting, but only one variable besides many other. I would rather look at the lift-over-drag ratio for various lift coefficients. Many people get bogged in SEP charts (also called E-M charts frequently) and compare sea level thrust.
I started issue of Cl vs M because people are fooling around comparing fighter’s turn rates, etc. One can not compare these things w/o knowing these curves.
I talked about “useless theory” and practice because (besides other things) stall is not defined with max theoretical lift but usually by dyn.instability (see quoted book).
Also, many older configurations have excellent L/D ratio at cruise and in turns, but not at transonic speeds. Dynamic installed thrust is different thing than static. Engine cycle matters as well as ECS. That’s why I talked about g vs Mach diagrams.
Nowadays kids can collect more official graphs than Intelligence Agencies. Maybe latter are not more interested in these things but in putting puppet governments.
adriannI used to use these as ref when i read for a degree. Unfortunately aerodynamics isnt really a subject featuring samba bands and gogo dancers.
Thank you all for advices, I’ve red all quoted titles but I’m still waiting for somebody to put actual Cl vs Mach graph !
adriannI wanted to say that some professor at our (and other) university could give us one actual graph of real airplane. It is easy to write formulas devised half a century ago.
I do not rate books you mentioned, useless. Very fine and interesting books. One’s whole life is inside.
Still you didn’t attach any actual graph for actual plane because there is none. Somebody name a plane and put it’s diagram !
adriannThe 21 interceptor is built in quest for Mach 2.0. In earlier pilot’s and tactic manuals one was not supposed to engage afterburner below 5 km altitude, except on TO. Performances are calculated and presented for altitudes from 5 to 15 kilometers.
Speed was not to drop below 350-450 km/h depending on model and weight. Alpha was to be kept below designated on indicator, with margin to the stall.
Lately discovered ‘fighter’ abilities were result of their design tradition for high T/W and low wing loading.
adriann[QUOTE]
Dare2
“As is the case for most Russian designs up to the 29, rearward visibility was quied bad too, in fact the cockpit was very small and it was hard for a Mig Jockey to look for threats around him, let alone under any load factor.”
I didn’t mention rearward visibility because even nowadays many manufacturers opts for more fuselage volume instead of it.
Schorsch
“The SR-71 has its drag peak behind Mach 1. The drop specific range compared to the increase in speed is not really desirable, so wouldn’t do anything like crediting it with the infamous “supercruise”. The SR-71 actually supercruised, it had better specific range at Mach 3 than at Mach .9.
You are offending McDonnel and its Phantom. The subsonic cruise performance of the MiG-25 was a disaster due to the engine, which had a energy efficiency like an open camp fire at subsonic speeds. The MiG-25’s engine basically uses similar principles as the J-58, it is less radical though and a more practical solution. When flying at M.85, the MiG-25 is a sitting duck, it can’t even run (up to M1.8 its acceleration will be worse than that of a Phantom).”
I meant just hypothetically that SR-71 could cruise at M 1.1. It wasn’t important for it. That dictates engine cycle and slim a/c profile. All sonic a/c has Cd peak at ~ M 1.1.
MiG-25/F-4. Phantom will forgive me…I remember when MiG landed at Hakodate, Japan in ’76. Most secret fighter. You’re wright about it’s engine efficiency at B737 speeds, at Mach 2 they are far more efficient than all except SR-71’s. Some day it’s performance will be explained.
“LoD of 12 is even above F-16 level, rather take 10 as ballpark for 4th generation. 3rd generation between 8 and 10 (F-4: 8.6, F-104: ~9).”
I meant SST’s L/D. You’re wright about fighter’s (F-16/MiG-29 ~ 10.5, F-14/MiG-23 15/12 spread, 7.5/6.4 swept, MiG-21 ~ 8…)
Sens
“Something done in desperation and still killed in the end.
By all admiration for the MiG-21s and the ease to fly that, it still has some “coffin-corners” in the flight envelope. Find out by evaluations later and from reports of Israeli pilots, when they got not the claimed kill, but were just credited with a squadron-kill only.
The first MiG-21s had a similar high accident rate like the GAF F-104G, but that was operated at low level mainly!
The GDR had 120 MiG-21s of the first generation. From that 39 were lost by accidents and 20 pilots killed.”
You are wright about accidents. It was usual for that a/c configurations, high landing speed on the back of the (huge)drag curve (negative speed stability), poor engine response for go-around..
I didn’t mean that 21 is wonder a/c. And I wouldn’t believe official kill-ratio claims. Too much politics/moral.
sainz
“Have we any usable statistics about G’s at gun-kills at Mid-East and in Vietnam ?”
I don’t or I didn’t pay attention. I imagine that many are done with “gum-sights”. I think that one could not care about all that limitations: gyro, radar, missile gyros, launch rails, engine at launch, alpha at lounch…one should have had Cray computer instead of head.
adriannI can’t think of an airframe that has an LoD about 8 in supersonic. The one that has the mentioned 8 is the Concorde.
The SR-71 didn’t do anything in Dry Thrust, but don’t overrate that: the engine of the J-58 was special. Although it needed A/B for anything but taxiing, it still achieved better specific range at Mach 3 than at Mach .9 (that’s why the SR-71 went to Mach 3 when possible, even on ferry flights).
You are wright, I wasn’t precise. L/D 12 is best L/D (subsonic), but at M 2.0 their figure is about 7.3 – 7.5 compared to usual fighter’s 4. I think SR-71 could also fly slightly above M 1.0 in military thrust, after short dive and pull-up, to save fuel and time (L/D 11.5 and 6.5 at M 3.0, wing t/c 2.5 %, chines and fuel transfer to unload elevons).
MiG-25 is different story, rugged but practical. It will be seen that usual performance (M 0.9) are in F-4C class but with that capability replied at M 2.0+ at high altitude where others fights for 1g.
adriann[QUOTE=Dare2;1503044]
Some Russian would have, i can remember a video where a Mig 21 pilot was trying to evage the IAI world’s top ace fighter Giora Even Epstein and pulling maneuvers no one thaught were possible with the Mig.
You all guys are really something, either truly professionals or enthusiasts with deep knowledge.
This Egyptian pilot maneuver intrigued me also so I found out in cited book, how it was possible. It was unexploited capability, out off flight manuals, probably incidentally discovered, in the class of MiG-29, F-15/16 but with limits. I have heard that in mock combat in the US, F-15 has hard times with 21 at low speeds, because of latter’s pitch pointing ability. Of course, that was not available to MiG-21 users ie manuals.
I think 21’s real limitation is only pilot’s forward and side field of view. You can read in 21F’s manual that it can sustain 5g at 5 km altitude !? Limited range, wing span..had most it’s generation fighters. Other’s gyro-gunsights also toppled at ~3g, some like F-4C/D didn’t have it at all for podded canon, AIM-9 and radars had officially similar restrictions…
adriann[QUOTE=alfakilo;1502635]
“I have no idea what you are trying to say with that statement. If you are suggesting that the F-104 would buffet at transonic speeds when pulling g, you are misinformed.”
I wanted to say that because of laws of physics every airfoil experience shock induced buffet, thinner and sharper one – less, fastest a/c with their t/c ratio 2.5 – 3.0 % the least, at low altitude ! At high alt where a/c flies at high alpha, LE flaps helps but not enough.
“At low altitude (5000′), average weight, two missiles, full burner…the F-104G will sustain about 6gs at about 420KIAS. For example…
But before I address the rest of that, let me ask you this…
Have you ever flown the F-104G?”
Unfortunately I didn’t have that privilege to fly it. But it is classical energy fighter that is excellent with guns only combat. If angles fighter has a useful missile, that’s it. Otherwise, MiG-25 would be unbeatable, it is like 104 but two steps more. Similar to 104 is unslatted F-4. For their generation high sustained turns (peak at ~ M 0.9). As indicated airspeed is lowering advantage melts rapidly. What about famous F-14? Underpowered (not much of energy fighter), but fine lift, drag at lift and controllability. It survived against F-4J? Neither F-18 excels in SEP. It beats others when forces them to slow-down.
But 104 didn’t deserve to someone speaks bad for it. Lancer tells about it’s weaknesses.
adriann[QUOTE Mirage IV, Tu-144
F-4, F-104G [/QUOTE]
Don’t argue hard, gentleman…there is true in all opinions.
I think, Mirage IV supercruise (with AB) is account on large internal fuel capacity, similarly to B-58 cruise. The F-4 is limited to 30 min in AB but fuel drops faster.
The Concorde and Tu-144 are different story. The finest Lift to Drag ratio (~12) allows supercruise without AB. I wonder what about SR-71’s military thrust cruise ?
I learned a lot about max speeds of fighters in mentioned book. It came out that record flights are usually achieved with specially polished airframe, engines chosen with upper manufacturing tolerances (higher thrust), particular atmospheric conditions (higher temp gives higher TAS for the same allowed CAS), or pushing it slightly beyond limit what exponentially shortens service life.
Of course that F-104 is fine aircraft, with its limits. At transonic speeds (above say Mach 0.8) every airframe experience some shock buffet that is heaver with higher lift (or alpha, G). The Starfighter turns fine at low altitude, above 450 kt speed. But limitations are instantaneous turns, speed loss in turns at lower CAS (that is even at higher speed at medium to high altitudes) and handling, especially because unfavorable pitch/yaw to roll inertia ratios, not to mention high tailplane effects.
adriannForgive me for interfering…for Mach >1.0 one needs most or all of: tremendous military thrust to weight ratio, low wing thickness to chord ratio, low aspect ratio, proportionally small wing (F-104 like)… Most of these affects adversely flight characteristics and other performance and none of ’50s and ’60s fighters in spite of this flew above M 1.0 in operational configurations.
adriannDoes somebody knows similar book about other fighter planes ?
adriannInteresting thread!
Energy charts are not something new…here’s a chart from 1940 showing Spitfire data:
Now, please understand…EM data never won a dogfight! But the info in this data often provided the pilot with excellent info on where best to fly his jet and where the enemy had the advantage.
Thank you for your efforts. Little education is welcomed. Nice graphs, but only Spit’s is somewhat official. Others are hypothetical and fiction. It is hard to find Eastern graphs in Western format like that of “MiG-21”.
I think Colonel Boyd put these graphs in most readable format, like that in last ‘michael82’ reply. Is it true ?
adriann[QUOTE=Dare2;1500732]LOL! I think active AdlA specialists knows a few things you don’t. 😀
And about the Mig-21, my instructor who flew the two seater at Reims in 1973 with the Normandy-Niemen squadron was impressed by its performances.
The Mirage III had probably better supersonic characteristics though…
Thank you for your reply. Figures said that Mirage could compete only with J79 or similar thrust class engine. Anyway, I think it’s a beautiful all-around aircraft.
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