Here’s why the SR-71 inlets had to be labeled “L” and “R” and why the Blackbird had engine and afterburner fuel control cable pulleys

Did you know a Blackbird was damaged after its engines were placed in the wrong inlet (So, the SR-71 inlets had to be labeled “L” and “R”)?

By Linda Sheffield Miller
Mar 29 2024
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The SR-71 Blackbird

The SR-71, unofficially known as the “Blackbird,” was a long-range, Mach 3+, strategic reconnaissance aircraft developed from the Lockheed A-12 and YF-12A aircraft.

The first flight of an SR-71 took place on Dec. 22, 1964, and the first SR-71 to enter service was delivered to the 4200th (later 9th) Strategic Reconnaissance Wing at Beale Air Force Base, Calif., in January 1966.

SR-71 T-Shirts
CLICK HERE to see The Aviation Geek Club contributor Linda Sheffield’s T-shirt designs! Linda has a personal relationship with the SR-71 because her father Butch Sheffield flew the Blackbird from test flight in 1965 until 1973. Butch’s Granddaughter’s Lisa Burroughs and Susan Miller are graphic designers. They designed most of the merchandise that is for sale on Threadless. A percentage of the profits go to Flight Test Museum at Edwards Air Force Base. This nonprofit charity is personal to the Sheffield family because they are raising money to house SR-71, #955. This was the first Blackbird that Butch Sheffield flew on Oct. 4, 1965.

The Blackbird was in a different category from anything that had come before. “Everything had to be invented. Everything,” Skunk Works legendary aircraft designer Kelly Johnson recalled in an interesting article appeared on Lockheed Martin website.

SR-71 Blackbird damaged after its engines were placed in the wrong inlet

There are so many interesting facts about the legendary Blackbird.

Here’s why the SR-71 inlets had to be labeled “L” and “R” and why the Blackbird had engine and afterburner fuel control cable pulleys
SR-71left inlet labeled “L”

When I used to walk around the SR-71 with my father, Butch Sheffield (former Blackbird RSO), he would point to the “L” on the one inlet of the SR-71 and smile and say, “Minter.” Colonel Minter ordered that every SR-71 in the inventory be labeled to make sure that It was clear which was the left from the right.

Early in the Blackbird program, a mishap happened on SR-71 #964: damage was done to the engines when they were placed in the wrong inlet.

Former crew chief Floyd Jones elaborates more on the story;

‘They will fit, but they are canted outboard instead of inboard. It happened on 964; she flew with no problem until checking the inlet’s major damage on spikes and center body also FOD the engine.

Here’s why the SR-71 inlets had to be labeled “L” and “R” and why the Blackbird had engine and afterburner fuel control cable pulleys
SR-71 right inlet labeled “R”

‘Reason it happened was they did something out of the usual. Both spikes were left on one side of the hangar. Usually, when a spike was removed was left on that side of hangar.’

Engine and afterburner fuel control cable pulleys

John Olp, SR-71 engine expert, told me something I’d never heard before about the cutting-edge engineering of the Blackbird.

‘The right engine throttle linkage was connected to the afterburner fuel control, and the left engine throttle linkage is connected to the main fuel control!

‘The aircraft throttle linkage was connected to the afterburner fuel control on the left engine and the main fuel control on the right engine (inboard side of the engines).

Here’s why the SR-71 inlets had to be labeled “L” and “R” and why the Blackbird had engine and afterburner fuel control cable pulleys
SR-71 Blackbird engine and afterburner fuel control cable pulleys.

‘It absolutely did matter because of the two different functions.’

Olp adds more details;

‘The two fuel controls were interconnected by a pulley and cable system in order to be fully synchronized. There was a pulley on each fuel control with a steel braided cable running underneath the engine, around more pulleys, so that, whatever position you set one fuel control at, the other one moved with it!

‘Afterburner fuel control on the right, main fuel control on the left. The aircraft throttles were connected to the threaded portion sticking out of the pulley shaft.’

Afterburner fuel control on the right, main fuel control on the left

SR-71 print
This print is available in multiple sizes from AircraftProfilePrints.com – CLICK HERE TO GET YOURS. SR-71A Blackbird 61-7972 “Skunkworks”

So today when you visit an SR-71, walk up to the inlets and look for the “L” or the “R” and you will know a little story about why they are marked left and right.

And remember! On the Blackbird the afterburner fuel control is on the right, the main fuel control is on the left.

Be sure to check out Linda Sheffield Miller (Col Richard (Butch) Sheffield’s daughter, Col. Sheffield was an SR-71 Reconnaissance Systems Officer) Twitter X Page Habubrats SR-71 and Facebook Page Born into the Wilde Blue Yonder Habubrats for awesome Blackbird’s photos and stories.

Photo credit: William Franklin Cely, Linda Sheffield Miller, John Olp and U.S. Air Force

Lockheed SR-71 Blackbird model
This model is available in multiple sizes from AirModels – CLICK HERE TO GET YOURS.

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Linda Sheffield Miller

Linda Sheffield Miller

Grew up at Beale Air Force Base, California. I am a Habubrat. Graduated from North Dakota State University. Former Public School Substitute Teacher, (all subjects all grades). Member of the DAR (Daughters of the Revolutionary War). I am interested in History, especially the history of SR-71. Married, Mother of three wonderful daughters and four extremely handsome grandsons. I live near Washington, DC.

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