# SR-71 Blackbird, what's that red outline on it's back? **URL:** \ **Category:** Factual Questions\ **Created:** [March 18, 2017, 2:03am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459 "2017-03-18T02:03:08Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![chacoguy](https://avatars.discourse-cdn.com/v4/letter/c/50afbb/32.png) [@chacoguy](https://boards.straightdope.com/u/chacoguy)\ **Post date:** [March 18, 2017, 2:03am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/1 "2017-03-18T02:03:08Z")
[See here.](https://img.rcgroups.com/http://site.nitroplanes.com/EDFnew/sr71a.jpg?h=IuW7bL45h0K9IpyXYhjHdA) I’m pretty sure that’s just a model, but I think it’s accurate. What’s that outline for? ---
**Author:** ![snfaulkner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snfaulkner/32/433_2.png) [@snfaulkner](https://boards.straightdope.com/u/snfaulkner)\ **Post date:** [March 18, 2017, 2:05am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/2 "2017-03-18T02:05:24Z")
Paint? ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [March 18, 2017, 2:10am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/3 "2017-03-18T02:10:25Z")
[Here’s the real thing.](https://upload.wikimedia.org/wikipedia/commons/9/97/Lockheed_SR-71_Blackbird.jpg) The model is missing the red outline around the in-air refueling port. WAG-it helps the pilot of the flying fuel tank line up the hose. ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [March 18, 2017, 2:15am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/4 "2017-03-18T02:15:20Z")
> [@running\_coach](#): > > [Here’s the real thing.](https://upload.wikimedia.org/wikipedia/commons/9/97/Lockheed_SR-71_Blackbird.jpg) The model is missing the red outline around the in-air refueling port. > > WAG-it helps the pilot of the flying fuel tank line up the hose. [Boy, was I wrong.](http://en.citizendium.org/wiki/SR-71_Blackbird) > [@](#): > > The red stripes found on some SR-71s are there to prevent maintenance workers from damaging the skin of the aircraft. The curved skin near the center of the fuselage is thin and delicate. There is no support underneath with exception of the structural ribs, which are spaced several feet apart. ---
**Author:** ![Debillw3](https://avatars.discourse-cdn.com/v4/letter/d/3bc359/32.png) [@Debillw3](https://boards.straightdope.com/u/Debillw3)\ **Post date:** [March 18, 2017, 2:16am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/5 "2017-03-18T02:16:58Z")
> [@running\_coach](#): > > [Here’s the real thing.](https://upload.wikimedia.org/wikipedia/commons/9/97/Lockheed_SR-71_Blackbird.jpg) Am I seeing correctly that there’s some kind of notation on the inside of the line? It looks fuzzy, but it seems more pronounced (like letters or numbers) than a standard dashed line would be. ---
**Author:** ![snfaulkner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snfaulkner/32/433_2.png) [@snfaulkner](https://boards.straightdope.com/u/snfaulkner)\ **Post date:** [March 18, 2017, 2:19am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/6 "2017-03-18T02:19:48Z")
> [@running\_coach](#): > > [Boy, was I wrong.](http://en.citizendium.org/wiki/SR-71_Blackbird) Whoa! Good find! Never woulda guessed that. ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [March 18, 2017, 2:21am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/7 "2017-03-18T02:21:36Z")
> [@Debillw3](#): > > Am I seeing correctly that there’s some kind of notation on the inside of the line? > > It looks fuzzy, but it seems more pronounced (like letters or numbers) than a standard dashed line would be. Looks like a [chart for model makers.](http://web.ipmsusa3.org/sites/default/files/reviews/sr-71-blackbird-d-21b-drone/hasegawasr-71blackbirdwithd-21bdronedecals.jpg) It says “no step”. ---
**Author:** ![Debillw3](https://avatars.discourse-cdn.com/v4/letter/d/3bc359/32.png) [@Debillw3](https://boards.straightdope.com/u/Debillw3)\ **Post date:** [March 18, 2017, 2:28am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/8 "2017-03-18T02:28:00Z")
> [@running\_coach](#): > > Looks like a [chart for model makers.](http://web.ipmsusa3.org/sites/default/files/reviews/sr-71-blackbird-d-21b-drone/hasegawasr-71blackbirdwithd-21bdronedecals.jpg) It says “no step”. Ah, thank you! That makes sense in terms of your above revelation. ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [March 18, 2017, 3:47am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/9 "2017-03-18T03:47:45Z")
Am I the only one that’s a little bit disappointed that the cool red stripe is just a “NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP” sign? Must be why they [left off](https://sacmuseum.org/wp-content/uploads/2016/03/SR71_2.jpg) the words for the museum plane. ---
**Author:** ![snfaulkner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snfaulkner/32/433_2.png) [@snfaulkner](https://boards.straightdope.com/u/snfaulkner)\ **Post date:** [March 18, 2017, 3:51am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/10 "2017-03-18T03:51:27Z")
I’ll take a purposfull “no step” stripe over pointless racing stripes. ---
**Author:** ![Chisquirrel](https://avatars.discourse-cdn.com/v4/letter/c/6bbea6/32.png) [@Chisquirrel](https://boards.straightdope.com/u/Chisquirrel)\ **Post date:** [March 18, 2017, 3:56am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/11 "2017-03-18T03:56:28Z")
> [@snfaulkner](#): > > I’ll take a purposfull “no step” stripe over pointless racing stripes. On a Blackbird? That thing should have racing stripes ON TOP of it’s racing stripes. ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [March 18, 2017, 4:06am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/12 "2017-03-18T04:06:20Z")
> [@running\_coach](#): > > [Here’s the real thing.](https://upload.wikimedia.org/wikipedia/commons/9/97/Lockheed_SR-71_Blackbird.jpg) > [@Fubaya](#): > > Am I the only one that’s a little bit disappointed that the cool red stripe is just a “NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP” sign? Must be why they [left off](https://sacmuseum.org/wp-content/uploads/2016/03/SR71_2.jpg) the words for the museum plane. Your picture doesn’t have the ribbing in that area that mine does. Maybe the area was strengthened. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [March 18, 2017, 12:07pm UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/14 "2017-03-18T12:07:18Z")
> [@Fubaya](#): > > Am I the only one that’s a little bit disappointed that the cool red stripe is just a “NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP” sign? Must be why they [left off](https://sacmuseum.org/wp-content/uploads/2016/03/SR71_2.jpg) the words for the museum plane. Yeah, but it’s needed. Last time I was walking on a Blackbird I put my foot through the wing. Embarrassing. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [March 18, 2017, 3:11pm UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/15 "2017-03-18T15:11:38Z")
> [@running\_coach](#): > > [Here’s the real thing.](https://upload.wikimedia.org/wikipedia/commons/9/97/Lockheed_SR-71_Blackbird.jpg) The model is missing the red outline around the in-air refueling port. > > WAG-it helps the pilot of the flying fuel tank line up the hose. As you already found out, that was a bad guess. But there are indeed markings painted in front of boom-type refueling ports to help the boom operator calibrate his eyes. See [https://i.ytimg.com/vi/sL5MxCwkLJQ/maxresdefault.jpg](https://i.ytimg.com/vi/sL5MxCwkLJQ/maxresdefault.jpg) or [http://www.airfighters.com/articles/tanker/closing.jpg](http://www.airfighters.com/articles/tanker/closing.jpg) for a pretty good look at the various markings. They’re painted the same size on every USAF aircraft to give the boomer a consistent target regardless of the size of the receiver aircraft and the location of the port. I’m actually surprised to see the aiming stripes aren’t painted on your SR-71 photo. That \*may \*be an artifact of it being the two-seater and there isn’t the usual flat space just ahead of the receiving port. Any way they tried to “pour” the symbology over the curved surface would introduce distortion. I also bet that SR- refuelers were a dedicated fleet of tankers with a dedicated batch of boom operators. Who were highly experienced, hand-picked for skill, and would only have to contend with one type and shape of receiver for their entire assignment to the SR- refueling unit. So the lack of markings may not have mattered as much. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [March 19, 2017, 11:23am UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/16 "2017-03-19T11:23:37Z")
> [@snfaulkner](#): > > Paint? As I recall, paint was very difficult/expensive for the Blackbird. It flew so fast, the skin got real hot, and standard paints burned off in the first few minutes of flight 9possibly damaging the plane). > [@running\_coach](#): > > Your picture doesn’t have the ribbing in that area that mine does. Maybe the area was strengthened. Note that if you zoom in on the picture of it in flight, you can see wavy-looking spots on the plane. I’ve read that the skin of the SR-71 got so hot in flight (from friction with the air) that the metal skin actually distorted (like bacon on a griddle). That’s why it had to be made of titanium. Presumably it went back to the original shape when it cooled. (Or did the mechanics have to redo it after a few flights?) Interesting to actually see it. ---
**Author:** ![LH75](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lh75/32/4438_2.png) [@LH75](https://boards.straightdope.com/u/LH75)\ **Post date:** [March 19, 2017, 12:58pm UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/17 "2017-03-19T12:58:21Z")
> [@Fubaya](#): > > Am I the only one that’s a little bit disappointed that the cool red stripe is just a “NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP” sign? Must be why they [left off](https://sacmuseum.org/wp-content/uploads/2016/03/SR71_2.jpg) the words for the museum plane. That SR71 is in the SAC museum not far from here. [This is my daughter](http://s1217.photobucket.com/user/longhair75/media/IMG_0168.jpg.html) standing in front of that plane. It was the start point for a 10k she ran last spring. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [March 19, 2017, 1:52pm UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/18 "2017-03-19T13:52:03Z")
> [@Fubaya](#): > > Am I the only one that’s a little bit disappointed that the cool red stripe is just a “NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP NO STEP” sign? 😕 There is no cause for disappointment. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [March 19, 2017, 1:58pm UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/19 "2017-03-19T13:58:04Z")
> [@LSLGuy](#): > > …there are indeed markings painted in front of boom-type refueling ports to help the boom operator calibrate his eyes. See [https://i.ytimg.com/vi/sL5MxCwkLJQ/maxresdefault.jpg](https://i.ytimg.com/vi/sL5MxCwkLJQ/maxresdefault.jpg) or [http://www.airfighters.com/articles/tanker/closing.jpg](http://www.airfighters.com/articles/tanker/closing.jpg) for a pretty good look at the various markings. They’re painted the same size on every USAF aircraft to give the boomer a consistent target regardless of the size of the receiver aircraft and the location of the port. > > I’m actually surprised to see the aiming stripes aren’t painted on your SR-71 photo. That \*may \*be an artifact of it being the two-seater and there isn’t the usual flat space just ahead of the receiving port. Any way they tried to “pour” the symbology over the curved surface would introduce distortion… Your point about distortion is interesting, particularly about the training/skill of the boom operator in recognizing the iconic (spatialized) graphic. If all ports are the same spatial configuration this question doesn’t apply except in the extreme case of bizarre fuselages, one which the SR-71 would come close. One of the “distortions” that the operator, like all of us in life, is the relative size vis-a-vis _him_ with distance and angle [think amorphous writing on roadways], but I’m wondering about the following: Are the icons consistent/fixed size among themselves across all aircraft, or are they resized to have as consistent a match as possible, optically for the boom operator, to match the configuration of the port design? ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [March 19, 2017, 2:20pm UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/20 "2017-03-19T14:20:30Z")
**JHBoom** was a refueling boom operator on KC-10s. I’ll ping him. I had thought all USAF were painted the exact same and had written that into my post. While looking for example photos I found the F-16 markings I thought were universal were different on at least some other aircraft including the E-3 I linked to. So I changed my post to match. Let’s see what the real expert says. ---
**Author:** ![Randolph](https://avatars.discourse-cdn.com/v4/letter/r/e5b9ba/32.png) [@Randolph](https://boards.straightdope.com/u/Randolph)\ **Post date:** [March 19, 2017, 3:00pm UTC](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459/21 "2017-03-19T15:00:01Z")
> [@running\_coach](#): > > [Here’s the real thing.](https://upload.wikimedia.org/wikipedia/commons/9/97/Lockheed_SR-71_Blackbird.jpg) You can see the fuel weeping everywhere while the plane is still cool enough to have gaps in its panels. [Next page](https://boards.straightdope.com/t/sr-71-blackbird-whats-that-red-outline-on-its-back/782459.md?page=2)