SR71 Lecture – Colonel Richard Graham – RAF Museum Cosford

[Wander00]

Apparently he did some lectures at Duxford last weekend

[treadigraph]

The SR-71 was a seriously class act. Best to everybody who made it happen...

[oldpax]

I thought Vietnam was a conflict not a war?

[megan]

I thought Vietnam was a conflict not a war?

War is often known as armed conflict, and is a state of armed conflict between societies. It is generally characterized by extreme aggression, destruction, and mortality, using regular or irregular military forces. An absence of war is usually called "peace". Some parties may not recognise a conflict as a war, and is termed an "undeclared war".

[Shaggy Sheep Driver]

The SR-71 was a seriously class act.....

Not so sure about that. Have you read 'Sled Driver'? SR71 had to enter a dive to go supersonic (to overcome transonic drag), had to have one engine in 'burner when tanking, and suffered serious 'engine unstart' consequences that led to the loss of a sizeable proportion of the fleet, and to the deaths of many crews.

I consider it more a 'cobbled together by Kelly Johnson in a rush' solution to a pressing military requirement.

It did the job, but was not a 'carefree' aeroplane, as evidenced by its abysmal accident record.

[treadigraph]

20 of the 50 A-12/SR-71 airframes were lost over 25 years, a high ratio indeed, but remarkably only four crew died. One was unable to separate from his seat after ejecting, another drowned after opening his visor following ejection and a sea landing. The reasons for the losses were many; mid air collisions, landing accidents, instrumentation and wheel failures, etc - only one appears to have definitely been caused by an engine unstart.

[megan]

Nothing cobbled together about it. It pushed the technology boundaries on so many fronts. Losses,
SR-71
64-17957 Fuel cavitation
64-17965 INS platform failure
64-17966 subsonic high speed stall
64-17969 subsonic high speed stall
64-17970 Midair collision with tanker
64-17977 Wheel explosion on take off
64-17978 Landing accident
64-17974 Engine explosion, complete hydraulic failure
64-17954 Lost on runway
64-17953 Test flight
64-17952 Test flight
64-17950 Anti skid brake system evaluation
A-12
60-6926 Stall due incorrect pilot data display
60-6928 Training/test flight
60-6932 Lost off Phillipines
60-6939 Complete hydraulic failure
60-6941 Failure of D-21 drone launch
60-6929 Incorrect installation of SAS
60-6936 Fire fractured fuel line
60-6934 Landing

[porch monkey]

So SSD, after having your Concorde claim called out as complete B/S, that's what you come back with? Really? Perhaps you should do some reading of your own before further comment.

[megan]

suffered serious 'engine unstart' consequences that led to the loss of a sizeable proportion of the fleet, and to the deaths of many crews.

SSD has little knowledge as to the aircraft, there any number of good books available detailing the aircraft should he wish to educate himself. While unstarts were a feature of the aircrafts operation, there was only one crash and one death in which an unstart had a role to play.

That was 64-17952 on a test flight to establish, among other things, improving high Mach cruise performance by reducing trim drag. This entailed having the CoG further aft than normal to compensate for the rear ward movement of the CoP at high Mach. An unstart always produced a high pitching moment, and the pilot had to be right on top of it before the AoA exceeded a critical value where control would be lost, and be unrecoverable. Controlling the pitch rate proved not a great problem, as years of trouble free service proved. However in this particular case with an unstart, with the CoG so far aft it was not controllable, and control was lost, with the entire forebody breaking away from the main body.

The solution to reducing the trim drag was to move the CoL forward, so reducing the static margin and trim drag. This was achieved by inserting a wedge between the nose section and the forward fuselage, giving the nose a 2° tilt up.

[Vzlet]

"...only 10-15 people..."?

Paracab, thanks for your recap of what's always a fascinating subject.

I'm not sure of the context of this statement:

For the duration of each mission, it was likely only 10-15 people knew they were airborne...

but taken literally the number was certainly far higher than that. It took a large number of people to prepare the crew and the aircraft for flight. Tanker support was the norm, and often involved multiple refuelings. SR-71s (and the intelligence products they enabled) were valuable assets and considerable external efforts were devoted to help ensure every mission's safety and success. Two guys with their space-suited butts on the line, but a big team behind them. On the other side, frustrated bad guys in large numbers along the mission route were routinely aware of its presence. Adding those factors together, I think a good argument could be made that, on a per-flight basis, an SR-71 attracted more total attention than any other aircraft.

SSD - The "dipsy doodle" was simply the most efficient means of transiting a high-drag region 1400+ kts below the normal operational speed for which the aircraft was optimized. No shame in that!

[treadigraph]

there was only one crash and one death in which an unstart had a role to play

And the other crew member survived. I don't believe both crew members died in any of the 20 losses (think most of the A-12 crashes were pilot only test flights/missions).

[Shaggy Sheep Driver]

Not MY claim, Porch Monkey? I suggest you re-read the post.

With 2/5 of the airframes lost to 'accidents' I don't think it was quite the technical marvel one or two on here are claiming.

Furthermore, its susceptibility to engine unstarts (indicative of an unsophisticated intake design), the need for exotic fuels, the need to dive through transonic drag (inability to get through 'the sound barrier' in level flight, never mind in a climb) all point to a relatively undeveloped aeroplane.

Perhaps had Kelly Johnson had a lot more time and dollars, and no pressing deadline from his military customer, he might have got it right.

[Herod]

Perhaps had Kelly Johnson had a lot more time and dollars, and no pressing deadline from his military customer, he might have got it right.

Then it would have been "totally awesome", as opposed to just "awesome"

[megan]

SSD, you again show a lack of understanding. The unstart problem was not the result of "unsophisticated intake design" as you put it. The intake design was incredibly sophisticated, the problem was the state of the art at the time in controlling the intake parameters. This problem was later solved with the invention and adoption of digital computers to manage the parameters.

the need for exotic fuels

So what fuel do you suggest could have withstood the operating environment? Wood or coal perhaps?

(inability to get through 'the sound barrier' in level flight

Wrong. The dive procedure was to get through the exceptionally high drag of the flight envelope in the most expeditious manner. Expeditious in this context is as quickly as possible and with the lowest fuel burn.

The accident rate is indicative of an aircraft that is operating at the very margins, mechanically, aerodynamically, technologically. That's why not everybody got handed the keys.

You best do some reading.

[treadigraph]

I recommend "Skunk Works" by Ben Rich and Leo Janos, very readable (ie, not too tech for me!) and covers development of U-2, SR-71 and F-117.

Good PPRuNe thread on Concorde which also touches on SR-71 intakes and unstarts. Via a very quick skim, I got the impression that Concorde's development team greatly admired the SR-71.

I guess avoiding spilled champagne wasn't an issue Kelly Johnson had to consider for those aboard the SR-71.

A little over four years from clean sheet to airborne by a relatively small team from Lockheed and the P&W guys, followed by an almost unbroken 37 years of flying by A-12s and SR-71s is an incredible achievement. It seems military politics grounded it, not any airworthiness or age issues.

[Shaggy Sheep Driver]

I've read both 'Skunk Works' and 'Sled Driver'. Both of these books have informed my posts on here. It was a machine of amazing performance, but a flawed machine. A military compromise between performance, cost, crew safety, and time to develop.

[megan]

but a flawed machine

In what was it flawed, and how would you have overcome those flaws? Have a read of the link before offering an opinion.

Neither the "Skunk Works" or "Sled Driver" give a real insight into the aircraft. Mostly I would recommend "Lockheed Blackbird - Beyond The Secret Missions" and "SR-71 Revealed". The very best though is available on line at http://ntrs.nasa.gov/archive/nasa/ca...0090007797.pdf

[Phoenix1969]

The very best though is available on line at http://ntrs.nasa.gov/archive/nasa/ca...0090007797.pdf

Thanks a lot for posting, Megan - fascinating read.

[Wageslave]

Coal was considered as a fuel at one stage in it's development, wasn't it?

SSD, you don't sound like someone with a great knowledge of aviation if you think the SR71 "flawed". Do you have any conception of the difficulties of operating at the parameters required? Or the difficulties in engineering to achieve them? Unlike many contemporary military types it didn't have particularly unpleasant handling characteristics and many if not most of the losses were down to "engineering" rather than handling, a sign of operating continuously at the boundaries of the possible.

[Shaggy Sheep Driver]

SSD, you don't sound like someone with a great knowledge of aviation

Well, maybe you're right. Perhaps I was wearing a blindfold and ear plugs during all those decades......?

Do you have any conception of the difficulties of operating at the parameters required? Or the difficulties in engineering to achieve them?

Um, yes.

The rest of your post is more believable. It bears out what I said earlier. What's 'possible' of course, in a difficult environment, depends on the tools available.