SR-71 BLACKBIRD

Performance Data
 
The SR-71 BLACKBIRD "SENIOR CROWN" was tested at EDWARDS AFB prior to transfer to Beale AFB in California. Only the A-12 "OXCART", YF-12A "KEDLOCK" and M-21/D-21 "TAGBOARD" combinations were flown and tested at Groom Lake. The A-12 was NOT a prototype aircraft for the SR-71 Blackbird Program.

I have been asked on numerous occasions by friends and SR Fans about the SR-71 Blackbirds Top speed. Figures in excess of Mach 3.5  up to Mach 9 have often been quoted on various WEB sites.

Below are my personal opinions on this subject with information supplied from the Blackbird Flight Manuals and people within the Blackbird community ( Pilots/ Engineers/ Commanders) who I know personally.

I have looked at a some areas to try and dispel that the Lockheed SR-71 Blackbird ever flew above Mach 3.32.  Areas that I have looked at are a Typical SR-71 flight  ( TABLE 1) , with corresponding  KEAS, KIAS , altitude ,temperatures and both Forward and Aft Bypass doors selection. Also looked at the Compressor Air Temperature (CIT) at Mach 3.5 at 80,000 feet and using the US Standard Atmospheric Temperatures, Outside Air Temperature at this altitude of - 52.209 Centigrade ( TABLE 2 ).  

The temperature range was extended to +/- 15 degrees Centigrade of the -52 .209 Degree in one  Degree increments to take the table to show an upper/ lower limit of -37 C  to -67 Centigrade.    As can be seen  at all the variation in the Mach 3.5 speeds ( speed of sound changes with temperature only) at 80,000 feet the CIT Limit of 427 C is exceeded in all cases.

          Another  area that I have looked at is the Mission Recording System (MRS) where data from the Aircraft and systems are monitored and some printed out on graph paper after a mission to apprise the flight and performance of the aircraft and systems. ( TABLE 3 )

I have used the MRS printout ( Table 4 & 5 ) from the London- Los Angeles  Record speed run to verify what is printed . These charts I obtained from the National Air and Space Museum

I believe that all other SR-71 MRS printouts that were at Lockheed or the 9th Reconnaissance Wing at Beale A.F.B  have been destroyed.

 
  Table
   
Pratt & Whitney JT11D / J-58 ENGINE  
Typical SR-71 Flight Parameters: 1 & 2
Mission Recorder System (MRS) 3
Mission Recorder System Data Printout ( MRS) 4 & 5
Flight Instrument Panel  
Typical Mission Profile  
All of the Blackbird performance data has been declassified.  
My Points of View from the Temperature Table and MRS printouts above.  
Conclusions  
Blackbird Model numbers  
 

   Pratt & Whitney JT11D / J-58 ENGINE

The Pratt & Whitney JT11D/ J-38 was a 20 feet long ,4 .5 feet in diameter and weighed 6500 pounds bleed bypass Turbojet engine. Later versions of the engine produced 34,000 pounds thrust
In the early days they were very careful at the speeds achieved and I think that the top speed they achieved was slightly above 3.2 and very few of pilots admitted to more than 3.24.

I believe that Ken Collins admitted to 3.3 in the A-12 and that the NASA IP took several of his guest riders to 3.26 or 3.27.

 
Its my clear understanding that the temperature profile steepened so rapidly above 3.2 that pushing 3.25 could easily exceed the 427 degrees Centigrade CIT limit and could cause serious damage to the engines.
The 427 degrees C. was the number P&W guaranteed the integrity of the engine to withstand. 


Mach 5 --- No Chance, and I don't think that Mach 3.5 was every achieved due to engine limitations.
The variable-geometry inlets for the engines were quite complex and intricate. The most prominent feature was a hydraulically-actuated conical spike which was automatically moved forward or aft by the Air Inlet Computer as required to keep the supersonic shockwave properly positioned in relation to the inlet throat. Working in conjunction with a series of bypass ducts and doors, the spike prevented supersonic air from entering the inlet and maintained a steady flow of subsonic air for the engine. At Mach 3.2 cruise the inlet system itself actually provided 80 percent of the thrust and the engine only 20 percent, making the J58 in reality a turbo-ramjet engine
 

   The J-58 also had Exhaust Gas Temperature ( EGT ) control and a De-rich feature both of which were not

found on other jet engines.
 
The EGT was automatically adjusted by electrically trimming motors on each engine which were activated when the throttles were at full military power and controlled the EGT within 790-800 degrees  Centigrade..
 

If the EGT reached 860 degrees Centigrade the De-rich facility kicked in to adjust the fuel-to- air ratio to reduce the EGT to below 860deg C. Once this had been achieved the pilot could return the engine to normal running by re-arming the system.

Pratt & Whitney J58 Turbojet

The Pratt & Whitney J58 engine was a nine-stage, axial-flow, bypass turbojet originally developed in the late 1950s to meet U.S. Navy requirements. It was the first jet engine designed to operate for extended periods using its afterburner. The J58 generated a maximum thrust of 32,500 pounds -- more than 160,000 shaft horsepower -- and was the most powerful air-breathing aircraft engine yet devised.

The J58 was specifically tailored for operation at extreme speeds, altitudes, and temperatures, and was the first aircraft engine to be flight qualified for the Air Force at Mach 3. At maximum output the fuel flow rate in the J58 is about 8,000 gallons per hour and the exhaust-gas temperature is around 3,400 degrees. The J58 was only used on the Lockheed YF-12 interceptor and its descendents, the A-12 and SR-71.

The J58 required the use of a special AG330 engine starter cart to spool the engines up to the proper rotational speed for starting. The cart was powered by two unmuffled Buick Wildcat V-8 racing car engines which delivered a combined 600 horsepower through a common gear box to the starter drive shaft of the aircraft engines. The J58s had to be spun up to about 3,200 RPM for starting.

The variable-geometry inlets for the engines were quite complex and intricate. The most prominent feature was a hydraulically-actuated conical spike which was automatically moved forward or aft by the Air Inlet Computer as required to keep the supersonic shockwave properly positioned in relation to the inlet throat. Working in conjunction with a series of bypass ducts and doors, the spike prevented supersonic air from entering the inlet and maintained a steady flow of subsonic air for the engine. At Mach 3.2 cruise the inlet system itself actually provided 80 percent of the thrust and the engine only 20 percent, making the J58 in reality a turbo-ramjet engine.

At the speeds the SR-71 operated, surface temperatures were extremely high due to aerodynamic heating: 800 degrees at the nose, 1,200 degrees on the engine cowlings, 620 degrees on the cockpit windshield. Because of the operating altitudes, speeds, and temperatures, Lockheed designers were forced to work at the cutting edge of existing aerospace technology, and well beyond in many cases. Many features and systems simply had to be invented as they were needed, since conventional technology was inadequate to the task. New oils, hydraulic fluids, sealants, and insulations were created to cope with the ultra-high temperatures the craft would encounter. A new type of aviation fuel, JP-7, was invented that would not "cook off" at high operating temperatures, having such a low volatility and high flash point that it required the use of triethylborane as a chemical ignitor in order for combustion to take place. The fuel itself was rendered inert by the infusion of nitrogen and then circulated around various components within the airframe as a coolant before being routed into the J58 engines for burning.

 
Typical SR-71 Take Off and Flight Parameters:
 
Fuel
 
Yes the SR-71 Blackbird did leak fuel while on the ground but the air-air refuelling after take off was not due to a lack of fuel due to the leaks.
Sealing the fuel tanks was a major problem although 10 000 linear feet of sealant was used to seal the tanks. Tank expansion and contraction with temperatures in the range -60 Degs F to 600 Degs F being encountered the sealant had to be compatible with the Titanium and stand the airframe stretching /shaking  / shudders of unstarts, turbulence and taxi loads.

The sealant used was called Fluorosilicone which as a liquid was applied by spray guns and paint brushes and then cured on the ground using special heaters.

 
The SR-71 never took off on a mission with a full  80,000 lbs (nearly full yes) of fuel although the test bird at Palmdale infrequently did with 80,000 lbs when there was no Tanker available and the Test Flight was NEEDED to be preformed.
 
 After a period of time, maintenance noticed that the heavy weight T/O's were wearing wheels and tires and so at some point, the program shifted to lighter weight T/O's followed soon after with a KC-135Q top off. There were 3 fuel load setting that an SR-71 would take off with depending on the mission requirements. These were 45,000, 55,000 and 65,000 lbs of JP-7.
 
 
A fully loaded (80,000 lbs of fuel) SR-71 at sea level conditions, 86Degs F, out of Ground Effect ( >30 Feet ) the minimum aerodynamic control speed was well over 280 knots.
 
If there was an engine flame out during take off the aircraft would Yaw considerably into the flamed out engine. The only action would be to shut down the afterburner on the other engine which would mean there would be insufficient thrust to keep the aircraft in the air.
 
Result , one  bent /destroyed aircraft.  Try explaining that to the boss.
 
 
FUEL BURN GROSS WEIGHT OUTSIDE TEMP FUEL BURN

LBS PER HOUR

 MACH HEIGHT
           
  100,000 STANDARD (-69 DEG F) 38,000 3.0 70,000 FEET
  100,000 STANDARD (-69 DEG F) 36,000 3.15 70,000 FEET
           
  135,000 +10 DEC C 28,000 Accelerating from 1.25 30,000 ft to  3.0 at 70.000ft  
  135,000 - 10 DEC C 16,000 Accelerating from 1.25 30,000 ft to  3.0 at 70.000ft  
           
  100,000 +10 DEC C 44,000 3.15 70,000 FEET
  100,000 - 10 DEC C 35,000 3.15 70,000 FEET
           
 Deviation from standard day temperatures could affect the performance of the aircraft. As the outside temperature increased the SR-71 would slow down as the inlets did not function as efficiently due to the forward by-pass doors opening more, slowing down the climb rate during acceleration and requiring more thrust during cruise.

The Pilot was always monitoring the CIT gauge to compute Outside Air Temperature against Fuel consumption to stay on the Fuel curve.
 
 
 
HIGHLY RECOMMENDED BOOKS
   

"Flying the SR-71 Blackbird" book   By    Richard H Graham  USAF (Ret) 

MISSION PLANNING
PRE-FLIGHT ACTIVITIES
AIRCRAFT PRE-FLIGHT
COCKPIT/ INSTRUMENTS PRE-FLIGHT
STARTING ENGINES
BEFORE TAXIING
TAXING AND BEFORE TAKEOFF
TAKE OFF AND CLIMB
KC-135Q AND COLD TANKER RENDEZVOUS ( See Table 1 Below)
ACCELERATION TO MACH 3+ ( See Table 1 Below)
CRUISING AND MACH 3+
DECEL AND HOT TANKER AIR RENDEZVOUS
RECOVERY
DEBRIEFING
 
  ISBN  978-0-7603-3239-9

FROM ARCHANGEL TO SENIOR CROWN--- DESIGN AND DEVELOPMENT OF THE BLACKBIRD  

By   Peter W Merlin.
BLACKBIRD - A TECHNOLOGICAL CASE STUDY
FORM FOLLOWS FUNCTION - DESIGN EVOLUTION OF THE BLACKBIRD
NECESSITY IS THE MOTHER OF INVENTION , CONSTRUCTION AND MATERIALS
ABOVE AND BEYOND - BLACKBIRD PERFORMANCE
A UNIQUE RESEARCH TOOL-  NASA'S MACH 3 FLYING LABORATORY
LESSONS LEARNED
  ISBN  978-1-56347-933-5
   
 
INLET UNSTART
 The engine Forward Bypass Doors ( FBD ) on the top and bottom of cowling and were controlled by Air Inlet Computers ( AIC ) which responded to the duct pressure ratio ( DPR) inside each inlet and these doors started to open at Mach 1.4.  The AIC  was programmed to control  FBD's as tight as possible (closed) without causing other problems.

If these doors opened to much then the air which was being dumped/bypassed overboard,  increased  drag due to the slower bypassed air exited into the supersonic air-stream.  This drag would have an detrimental effect on aircraft fuel consumption.

 
In the case of an engine "unstart" which is an expulsion of  the supersonic shock wave from the inlet to the outside of which the cause could be the Spike or Forward Bypass door( FBD)  position or a combination of both. There was an automatic restart facility however if this didn't work there it would be  reset manually by the pilot.  If the problem was the Forward  Bypass doors the pilot could reset these manually and the Spike would still be running in automatic . If it was the spike causing the problem both the Spike and FBD would be reset/operated manually by the pilot.

 There were flight restriction flying in the manual mode- Height/ speed and bank angle and of course this increased the pilots work load.

The Aft Bypass Doors ( ABD)  were controlled by the pilot at one of 3 set positions and these worked in the opposite direction to the Forward Bypass Door's,  open the ABD's and the FBD's shut tighter, shut the ABD's and the FBD's opened They also had little effect on aircraft drag.
 

 

TABLE 1:

Position    
CLOSE 100 % OPEN  
B 50%    OPEN
A 15 %   OPEN
Flight Phase Mach Knots Equivalent Air Speed

( KEAS )

 KIAS Altitude

( feet )

 Forward Bypass Doors

 ( FBD)

 Compressor Inlet Temp

Degrees C

( CIT )

  Exhaust Gas Temp

Degrees C

( EGT )

 Aft Bypass Doors

( ABD's)

  
Climb

and

Acceleration

 

 

 0.90 450   30,000          
0.95     33,000         Start of "Dipsey Doodle"
                Exceed  1.05 Mach in the decent
1.00                
1.04 420-430     Start to open     If FBD open to much select ABD "A" Raise aircraft

nose
1.05 450   30,000         KEAS HOLD
1.10                
1.25 450   33,000   <40 830    
1.30 450 505 31,600   17      
1.40 450 512 35,000   29 805   Must Not Exceed 830 Degs C
1.50 450 517 37,900          
1.60 450 522 40.500   52      
1.70 450 527 43,000   68   SELECT   "A" When FBD move out of fully closed , set ABD
1.80 450 529 45,500   84      
1.90 450 532 47,800   100      
2.00 450 535 49,800   116   SELECT "B"  
2.10 450 537 51,800   134      
2.20 450 539 52,200   <150 deg C      
2.26 450 540 53,500 closed down to about 5%       KEAS Bleed starts
2.30 450 541 55,600   171      
2.40 450 542 57,400   192      
2.50 450 544 59,000   212      
2.60 450 546 60,800   235   SELECT "A"  
2.70 440 536 63,600   257   "A"  
2.80 430 527 65,800   280      
2.90 420 517 68,100   304      
2.95 420 510 70,000         KEAS Hold disengaged
CRUISE 3.00 410 507 70,500   328   Position "A" or "CLOSED"

Dependent on OAT / Speed wanted and FBD scheduled
  3.05 405 502 71,900   340    Set to "CLOSE" Depending on OAT
  3.10 400 497 72,900   353      
  3.15 395 492 74,100   366      
  3.20 390 487 75,300   380      
  3.24     80,000   <427      

 
Because of the high speed cruise, ambient air temperature may change abruptly as different air masses are encountered. Initially, if a constant altitude  is maintained, flight into warmer air mass will cause a decrease in Mach and KEAS, and the true airspeed (TAS) and Compressor inlet temperature (CIT ) will remain constant.  A higher TAS and CIT will result as the desired Mach Is re-established.  The opposite would occur as result if flying into a colder air mass. New cruise altitudes or speeds maybe required to compensate for effects of variations in ambient air temperature.
OAT = Outside Air Temperature

The Outside Air Temperature at 80,000  will have and effect on the J-58 engine efficiency and speed of sound ( Mach Number) as can be seen from the table below where the US Standard Atmospheric Temperatures OAT for 80000 feet (- 52.209 C) 

 
The below matrix does not justify or extend the Mach limits of the SR-71 BLACKBIRD
 

TABLE 2:

 

        Speed of Sound- Mach 1 Mach 3.24 Max Mach 3.29 Mach 3.30 Mach 3.5      
    Outside Air Temp   MPH KTS MPH KTS MPH KTS MPH KTS MPH KTS CIT DEGS F CIT DEGS C Over Max 427C By:
  15 -37.209   689.4 598.7 2233.6 1939.7 2268.1 1969.6 2275.0 1975.6 2412.9 2095.3 1000 540 113
  14 -38.209   687.9 597.4 2228.9 1935.5 2263.3 1965.4 2270.1 1971.4 2407.7 2090.9      
  13 -39.209   686.5 596.1 2224.1 1931.4 2258.5 1961.2 2265.3 1967.2 2402.6 2086.4      
  12 -40.209   685.0 594.8 2219.4 1927.3 2253.6 1957.0 2260.5 1963.0 2397.5 2081.9      
  11 -41.209   683.5 593.6 2214.6 1923.2 2248.8 1952.8 2255.6 1958.8 2392.3 2077.5      
Hotter By Degs C 10 -42.209   681.7 592.0 2208.8 1918.2 2242.9 1947.8 2249.8 1953.7 2386.1 2072.1 973 523 96
9 -43.209   680.6 591.0 2205.1 1914.9 2239.1 1944.4 2245.9 1950.3 2382.0 2068.5      
8 -44.209   679.1 589.7 2200.3 1910.7 2234.2 1940.2 2241.0 1946.1 2376.8 2064.0      
7 -45.209   677.6 588.4 2195.5 1906.5 2229.3 1935.9 2236.1 1941.8 2371.6 2059.5      
6 -46.209   676.1 587.1 2190.6 1902.3 2224.4 1931.7 2231.2 1937.6 2366.4 2055.0      
5 -47.209   674.3 585.5 2184.8 1897.1 2218.5 1926.4 2225.3 1932.2 2360.1 2049.3 943 506 79
4 -48.209   672.8 584.3 2180.0 1893.1 2213.6 1922.3 2220.3 1928.1 2354.9 2045.0      
3 -49.209   671.3 583.0 2175.1 1888.9 2208.7 1918.0 2215.4 1923.8 2349.7 2040.4      
2 -50.209   669.9 581.7 2170.4 1884.6 2203.9 1913.7 2210.6 1919.5 2344.5 2035.9      
1 -51.209   668.3 580.7 2165.4 1881.5 2198.8 1910.6 2205.5 1916.4 2339.1 2032.5      
Standard Temp at 80,000 feet -52.209   666.8 579.1 2160.5 1876.2 2193.8 1905.1 2200.5 1910.9 2333.9 2026.7 912 489 62
Colder By Degs C 1 -53.209   665.3 577.8 2155.6 1871.9 2188.9 1900.8 2195.5 1906.6 2328.6 2022.1      
2 -54.209   663.8 576.4 2150.7 1867.7 2183.9 1896.5 2190.5 1902.2 2323.3 2017.5      
3 -55.209   662.3 575.1 2145.8 1863.4 2178.9 1892.1 2185.5 1897.9 2318.0 2012.9      
4 -56.209   660.8 573.8 2140.8 1859.1 2173.9 1887.8 2180.5 1893.5 2312.6 2008.3      
5 -57.209   659.2 572.5 2135.9 1854.8 2168.9 1883.4 2175.5 1889.2 2307.3 2003.7 880 471 44
6 -58.209   657.7 571.1 2131.0 1850.5 2163.8 1879.1 2170.4 1884.8 2302.0 1999.0      
7 -59.209   656.2 569.8 2126.0 1846.2 2158.8 1874.7 2165.4 1880.4 2296.6 1994.4      
8 -60.209   654.6 569.8 2121.0 1846.2 2153.8 1874.7 2160.3 1880.4 2291.2 1994.4      
9 -61.209   653.1 569.8 2116.0 1846.2 2148.7 1874.7 2155.2 1880.4 2285.8 1994.4      
10 -62.209   651.6 565.8 2111.0 1833.2 2143.6 1861.5 2150.1 1867.2 2280.4 1980.3 850 454 27
11 -63.209   650.3 564.7 2107.1 1829.8 2139.6 1858.0 2146.1 1863.7 2276.2 1976.6      
12 -64.209   648.8 563.4 2102.1 1825.4 2134.5 1853.6 2141.0 1859.2 2270.7 1971.9      
13 -65.209   647.2 562.1 2097.0 1821.1 2129.4 1849.2 2135.9 1854.8 2265.3 1967.2      
14 -66.209   645.7 560.7 2092.0 1816.7 2124.3 1844.7 2130.7 1850.3 2259.9 1962.4      
15 -67.209   643.8 559.1 2085.9 1811.4 2118.1 1839.3 2124.5 1844.9 2253.3 1956.7 819 437 10

 
Section V page 5-5. "COMPRESSOR INLET TEMPERATURE (CIT)
"With both inlet guide vanes (IGVs) cambered, the maximum allowable compressor inlet temperature is 427 degrees C.  With an IGV in axial (IGV light illuminated), 150 degrees C must not be exceeded, and continued operation with CIT above 125 degree C is not permitted (approximately Mach 2.0)"
 

From the Flight Manual, Section V. pg 5-8:  MAXIMUM MACH

"Mach 3.2 is the design Mach number.  Mach 3.17 is the maximum scheduled cruise speed recommended for normal operations.  However, when authorized by the Commander, speeds up to  Mach 3.3 may be flown if the limit  CIT of 427 C is not exceeded”

 
Tactical Limits: High Compressor Inlet Temperature (CIT)    Present Limit or Restriction  - 427 Degrees C.
A temperature of 450 Degrees C is permitted with engine RPM within normal limits and Mach Number within Tactical Limit.   Report maximum CIT and Time above 427 Degrees C. One hour total accumulated time allowed per engine. Running at these CIT's would seriously reduce the safety margins of the aircraft.

The Tactical Maximum Mach Limit was 3.3 and this could / would be reduced to reflect parameters required for a particular type of failure or response.

Notes:

85,000 feet was the cruising altitude of the SR-71 but depending on Aircraft Temperatures, Outside Temperatures and Fuel load, flight could be higher than this, 87,500 has been quoted to me by one crew but the Tactical Limits were not exceeded and Ken Hurtley participated in a test flight to over 89,500 during a CAT11 test program.
During the planning of the Transcontinental Record run  this Temperature of 450 Degrees C was authorised for a maximum time of 30 minutes but not used as the Prime mission was to set the record and deliver the SR-71 to the museum. SR-71 THERMAL ENVIRONMENT, By Peter Law
 
 
P & W Guaranteed the engines up to 427 Degs C, Above that figure, then you were in the lap of the Gods.
FLIGHT ENVELOPE  - Click Image to enlarge

Mission Recorder System (MRS)
 
The MRS is an airborne, integrated, mission and maintenance data recording system that continuously monitors and records the performance of aircraft and payload systems and crew audio. The system has the capacity to record a total 12 continuous hours of data.   
 
The MRS monitors the operation of systems and equipment under pre-flight, flight and post flight conditions , permitting identifications of failures, impending failures and low performance.
 
Multiplex switches within the MRS Collect, on sequential time-shared basis, analogue signals representing the control, performance and health of various aircraft systems. A multiplexing circuit in the DAFICS collects analogue signals representing the functioning of that system, providing a stream of pre-multiplexed data to the MRS.

 

 
The ANS supplies the MRS with data in digital and analogue form.
 
Following flight, the airborne tape is copied then computer processed. Processed MRS Data is used for performance analysis and fault isolation of monitored systems and for reconstruction of a flight.
 
Following a flight the recorded data on the UNIT 500 Tape is copied using a mobile ground Formatter (MGFU) for reproduction of non-voice data and a tape cope unit (TCU) for crew voice reproduction.  The TCU tape is played back in a voice playback unit which provides crew voice audio on a tape or cassette.
 
The MGFU creates a computer compatible tape (CCT) of MRS recorded digital recorded data. The CCT is processed in a specially programmed general purpose computer which produces printouts on performance and conditions of MRS -monitored systems and equipment.  The computer also drives a plotter which produces analogue graphs( traces) of MRS Monitored signals.
 
 
TABLE 3:  
   
  Number of signals monitored
ENGINE 16
HYDRAULIC SYSTEM 13
DAFICS 58
FUEL SYSTEM 29
ENVIRONMENTAL CONTROL SYSTEM 16
ELECTRICAL SYSTEM 24
MRS 18
ANS-DIGITAL DATA REPRESENTING APPOX 100 PARAMETERS 100
MISCELLANEOUS 20
 

MISSION RECORDER SYSTEM DATA PRINTOUT ( MRS)
 
 
TABLE 4:      This is a portion of one of the MRS Graph for the London to Los Angeles Record run in 1976
  PARAMETERS
LEFT VERTICAL AXIS   Minimum Increments Maximum Actual Top data Recorded
  Aircraft Vertical Acceleration -G's 0.0 0.5 1.0 1.5+
  Engine Throttle Position - Deg 0 20 125 122
  Centre Of Gravity- % MAC 0 2 25 25
  Angle Of Attack- Deg 0 5 17.5 7.5
           
A: Mach Number 0 50 3.25 3.25
B: LEFT ENGINE CIT 0 50 375 430
B: RIGHT ENGINE CIT 0 50 375 425
           
BOTTOM  HORIZONTAL AXIS TIME- IN MINUTES 0 5 For Duration of Flight  
 

As can be seen there are 6 Parameters being monitored on this MRS graph.  From top to bottom they are, Aircraft Vertical Acceleration -G's, Engine Throttle Position - Deg, Centre Of Gravity- % MAC, Angle Of Attack- Deg and

Engine CIT  ( The Min/ Max Range  I have identified as B on the graph)

MACH Number  (The Min/ Max Range  I have Identified as A on the graph)

 
CIT:  The Left Engine can be seen to peak on a couple of occasions at 430 Degs C for less than 30 seconds ,while the Right engine CIT remains below 427 Degs C
Mach Number :  as can be seen from this graph the maximum speed achieved was 3.25 Mach

Other MRS Graphs covering other parameters are also printed after a mission.

 
TABLE 5:
 

 

The MAXIMUM LIMIT of the DAFICS signal to the instruments (TDI ) is Mach 3.5   ( SR-71 Pilots Flight Operation Manual Section 1 , 1-135)    and the graph above has been modified to show where the  Mach 3.5 limit would be .

the CIT Range has also been modified to show a range of  0 - 550 Degs C to tie in with TABLE 2 Over Temperatures. 

Again any CIT Over temperature would be recorded on this chart.

 
 
TRIPLE DISPLAY INDICATOR (TDI)
  TDI RANGE TDI PANEL  
  Min  Max MAX READINGS THAT WOULD EVER BE SEEN The TDI Shows TRUE DATA at Supersonic speed.
         
     
                   
      5 6 0    
  KEAS - KNOTS  
               
               
               
    0 9 9 5 0  
  ALTITUDE/FT  
               
               
      3. 5 0    
  MACH  
 
       
       
KEAS 0 599 The Maximum limit of the DAFICS signal to the TDI is 560 KEAS.
       
       
ALT / feet 0 109950 Above 100,000 feet the first digit is dropped off, so 109,950 becomes 09950.

109995 is the Maximum DAFICS Signal
       

 
Mach 0 3.99 The Maximum Signal Limit from the DAFICS to the TDI is Mach 3.50 .

 
It is quite possible that only speeds in the range of   0 - 3.25 Mach would be recorded on the MRS graph.   If this is the case there would be NO hard copy Confirmation of any speeds greater than Mach 3.25 .  

The same applies to other parameters from the TDI in that they would only be recorded in the ranges displayed on the MRS . 

But as can be seen from the above graph  for the London to LA Speed run , the ACTUAL C.I.T  of 430 degrees C is recorded and so it could be assume that any speed above Mach 3.25 is exceeded it would be recorded on the MRS Graph.
 
Also on landing the RSO would fill in a pre-printed flight form which listed  beside aircraft faults, Maximum Mach Number, Time above a certain Mach number, Re-Fueling Off Loads, Maximum Altitude , Centre of Gravity Settings. This form would be reviewed with the maintenance people at the debrief and questions asked by Specialist System Representatives  of both the Pilot and RSO.
 
   
FLIGHT INSTRUMENT PANEL
AIR SPEED - MACH METER: A combination airspeed and Mach Meter , operating directly from pitot-static pressure, is installed on the pilots instrument panel. The Airspeed and MACH values shown are indicated values as opposed to equivalent airspeed and true MACH displayed on the TDI.  A limit airspeed needle varies with altitude to show the KIAS limit corresponding to a preset KAES vs altitude schedule.

At subsonic speeds pilots flew the SR-71 Primarily in reference to the Indicated Air Speed ( IAS) Although as the speed increase this reference became more inaccurate due to the air being compressed into the Pitot Tube and the error increasing as the aircraft flew faster. At high speed and altitude the KEAS and Mach readings on the TDI were more indicative of aircraft performance and limitations.
 
 

DISTANCE MEASURING EQUIPMENT ( DME ) gave the number of miles travelled per minute and not Mach number or Knots.
 
TRIPLE DISPLAY INDICATOR (TDI ) :  The TDI on the instrument panel in each cockpit provides digital displays of airspeed (KEAS), pressure altitude and MACH  Number as computed by DAFICS.   The  MACH  number indication range is  0 -  3.99. The minimum indication at static condition normally varies from 0.11 to 0.2 MACH Number and the MAXIMUM LIMIT of the DAFICS signal to the instruments is Mach 3.5
 
The TDI knots equivalent airspeed ( KEAS) indication range is 0 to 599 KEAS. The minimum indication normally varies from 25 - 110 KEAS. The maximum limit of the DAFICS signal to the instruments is 560 KEAS.
   
SR-71 FRONT COCKPIT INSTRUMENTS SR-71 REAR COCKPIT INSTRUMENTS
YELLOW - TDI YELLOW - TDI
 GREEN -  AIR SPEED - MACH METER  

 

Typical Mission Profile

SR-71 Theater's of Operation.

 
Click image to enlarge

 
From an SR-71 Pilot
We always monitored and limited our speeds to the 427C CIT limits. A typical profile would be standard climb, L/O about 77,500, cruise at mach 3 to 3.2 and slowly climb as we burned off fuel. Would enter target areas about 80,500/3.0 and if SAM activity hot would accelerate to 3.2 and slowly climb ( would screw up the Fan Song Radar Tracking Computers trying to keep calculating the lead aim point if they did launch a SA-2 ). In colder than usual air I remember seeing 3.25 or so, but crews flying the north Barents Sea would see 3.3 and a scoochie bit more. The highest altitude I remember ( and it was not something I kept track of ) was most probably, and typically, 83,500 at S/D point coming home or after a long hot loop.
 

 
My Points of View from the Temperature Table and MRS printouts above.
   
  Both CIT and Mach numbers at all phases of the flight are recorded on the MRS Graph
   
  The MRS graph MACH Range is 0-3.25 and the if the top of the Range (3.25) is exceeded there are two possibilities

1: The Actual top speed up to Mach 3.5 (DAFICS Signal Limit) would be recorded---

2: Only the Top of the Graph Range of Mach 3.25 Would be recorded  ----

 
  High CIT 's would have shown In the MRS DATA and would have been printed on the MRS Graph out after a mission or test flight. The RSO Maintenance log would have also been reviewed by System Specialists .
   
  If the Outside Air Temperature was +/- 15 Degrees the standard Temperature for  80,000 feet The CIT of 427 Degrees Centigrade would have been exceeded by between 10 and 113 Degrees Centigrade as can be seen from Table 2 above
   
  These high CIT's would have resulted in engine / inlet damage and also possible damage to insulation of hydraulic lines and other wiring installations  plus possible inlet damage which would have been detected by the Lockheed / Pratt & Whitney Reps at any of the Detachments or Beale AFB and reported to the Det Commander and Wing Commander or Company representatives if being used during a test program.
   
  Engine damage would have made the aircraft unserviceable and not available as a Primary or  Back up aircraft  for any other missions that day or following days and leaving only one SR-71 Blackbird available for any missions . On a test program side this would result in delays to the testing  programs and could have a financial impact.
   
  Twin engine changes and any associated system , hydraulic /electrical lines etc) that required changing would not be an over night job.    One engine change would take approximately  6-8 hours followed by the trip to the run-up pad to check the engine/s out at Mil Power and Afterburner.
   
  Due to the limitations of the DAFICS Maximum Signal Limit no Speed greater than Mach 3.5 would show on the TDI, even though the TDI Mach Range is 0 - 3.99 Mach.

The TDI is the only accurate Mach data reading at Supersonic speed with the AIR SPEED/ MACH METER and DME being too inaccurate

 
   
   
CONCLUSIONS
A
 Outside Air Temperature at the operating altitude of 80,000 feet would be critical to the performance of the J-58 Engines and as can be seem from Table 3, hotter or colder temperatures than the standard at this height ( -52.209C ) would have resulted in Overheating of the Compressor Inlet Temperatures( CIT) and inlets.   Also at all phases of the flight from Acceleration and climb to altitude, the  J-58 engines would have to be performing correctly with Spike correctly position and all inlet doors on both engines tightly shut to ensure that there is no drag produced by bleed bypass air.

Drag would also have a effect on fuel consumption, reducing range and speed
 
B
  Any  Crew ( USAF, NASA, C.I.A ) would have been disciplined or even fired for allowing the high speed with resulting damage and jeopardising the aircraft availability to perform any further missions or tests.
 
C
I'm also sure that if higher speeds had been achieved  without any damage to the aircraft/ systems all relevant Data from the flight ( MRS - RSO Maintenance Log) would have reviewed and saved and passed on to ALL relevant parties for discussion and developments. And bear in mind the Blackbird program was under increasing De-activation pressure and this information would have helped the cause to keep it going. It is my understanding that was not the case as  the only MRS Data to survive is in the NASM for the London / Los Angeles Record Run in 1976
 
D
Way back, Lockheed did in fact explore the possibility of increasing the Mach number, however, the cost, metallurgy, temperatures involved,  the decision ended with the study only. I'm sure that with developments in today's technology the power plant and inlets could be made to work at higher temperatures and air flows and maybe is in use on some" Black Program" under development but that is another story.
E
Talk of Very  High Mach numbers would not be able to be confirmed due to the limitation of the DAFICS Maximum Signal Limit which was Mach 3.5.The TDI is the only accurate Mach data reading at Supersonic speed with the AIR SPEED/ MACH METER and DME being too inaccurate.
 

 
 
 
 
All of the Blackbird performance data has been declassified.

 

FLIGHT RECORDS
 
The maximum design cruise speed for all variants (A-12, YF-12, M-21, and SR-71) was Mach 3.2. Speeds slightly exceeding Mach 3.3 have been recorded during test flights. The speed was limited by structural temperature restrictions (compressor inlet temperature had to remain below 427 degrees C). The fastest NASA Blackbird flights reached Mach 3.27.
 
Fastest known flights: some later surpassed see below **


YF-12A (60-6936) – Mach 3.14 (2,070 mph), USAF, official, 1 May 1965
SR-71B (61-7956) – Mach 3.27 (2,158 mph), NASA, unofficial, 14 December 1995
A-12 (60-6928) – Mach 3.29 (2,171 mph), CIA, unofficial, 8 May 1965
SR-71A (61-7958) – Mach 3.32 (2,193 mph), USAF, official, 28 July 1976
 
The Blackbirds were designed to fly as high as 90,000 feet, but typically operated between 70,000 and 80,000 feet. The recommended maximum altitude for the SR-71 was 85, 000 feet. The A-12 could more easily attain 90,000 feet because the airframe was lighter (one crew station, shorter fuselage, less equipment).
 
Highest known flights: some later surpassed see below**

YF-12A (60-6936) – 80,257 feet, USAF, official, 1 May 1965
     SR-71B (61-7956)– 84,700 feet, NASA, unofficial, 18 October 1994
SR-71A (61-7962) – 85,068 feet, USAF, official, 28 July 1976
SR-71A (61-7953) – 89,650 feet, USAF, unofficial, 1968 (CAT II flight test)
A-12 (60-6932) – 90,000 feet, CIA, unofficial, 14 August 1965

 New York to London Speed Run 1st September 1974

Time Flown: 1hour, 54min, 56.4sec

Distance Flown: 3,461.528 statute miles

Speed Flown: 1,806.95 statute mi/hr.

London to Los Angeles Speed Run  13th September 1974

Time Flown: 3hour, 47min, 39sec

Distance Flown: 5,446.87 statute miles

Speed Flown: 1,435.59 statute mi/hr.

 

West Coast to East Coast of USA

(National Record-Speed Over a Recognized Course): Coast to Coast Distance: 2,404.05 statute miles, Time: 1 hr 07 min 53.69 secs, Average Speed: 2,124.51 mph

Los Angeles To Washington D.C.

(World Record): Distance: 2,299.67 statute miles, Time: 1 hr 04 min 19.89 secs, Average Speed: 2,144.83 mph

St Louis To Cincinnati

(World Record): Distance: 311.44 statute miles, Time: 8 mins 31.97 secs, Average Speed: 2,189.94 mph

Kansas City To Washington D.C.

(World Record): Distance: 942.08 statute miles, Time: 25 mins 58.53 secs, Average Speed: 2176.08 mph

Note:  The above records were confirmed on the 15th March 1990 after the initial release on the 6th March 1990.

Those released on the 6th were in the same corresponding order of 

2112.62 mph C to C ,

2153.24 mph LA to  DC,

2205.48 mph St L to Cin,

2242.48 mph Kan C to DC.

**
Altitude in Horizontal Flight

 SR-71A. World Absolute and World
Class Altitude Record for Horizontal Flight - 85,135 feet, surpassing the previous record of 80,257 feet set by a Lockheed YF12A in June of 1965.
SR-71 flown by Capt Robert C. Helt, Pilot and Major Larry A. Elliott, RSO.

 
Speed Over a Straight Course (15-25km)

 SR-71A. World Absolute and World Class
Speed Record over a 15/25 Kilometre Straight Course - 2,193.167 MPH surpassing the previous record set by a Lockheed YF12A Interceptor prototype in June 1965.
SR-71 Flown by Capt. Eldon W. Joersz, Pilot and Major George T. Morgan Jr., RSO

 
Speed Over a Closed Course (1000km)

World Absolute Closed Circuit Speed Record over a 1000 Kilometre Course 2,092 MPH, surpassing the previous Absolute Speed Record of 1853 MPH and the World Class Speed Record of 1815 MPH set by a Russian Mig-25 Foxbat in October, 1967.
SR-71 flown by Major Adolphus H. Bledsoe, Jr., Pilot and Major John T. Fuller
 

 

 
Since that 
Member Of:  

 
Blackbird Association U-2 / SR-71
Roadrunners Internationale U-2 / A-12 / YF-12A / M-21
Dragon Lady Association U-2
Supporter Of The 4080th SRW U-2 / RB-57D
     
 

 

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