In this amazing story ,after losing all hydraulic power of the aircraft , Captain Al Haynes guided the plane to the Sioux city, crashed but saved 185 of the 296 lives (United Airlines Flight 232-Sioux City, 1989). After this incident, NASA started to work on PCA systems.
Gordon Fullerton landed an F-15, using only engine power. How did the F-15 land while the airliner crashed? Since an airliner and a fighter jet have different engine positions honestly it would make more sense to me if the airliner made it to the ground but fighter couldn't because it has relatively greater distance between engines, so better capability of yawing and as a result of having a shorter wingspan a fighter needs to fly faster to stay airborne. I understand the weight difference, i understand the possibility of adverse weather conditions during 232 flight, but i still don't get how a fighter is more capable than an airliner.
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3$\begingroup$ I think in the SUX incident they had directional control down. The problem was lack of flaps, air brakes, spoilers, brakes or reverse thrust. They touched down at over 200 kt and 1800 ft/min sink rate. Haynes tried to throttle up at the last minute to attempt some kind of a flare, but one engine responded quicker than the other causing a roll that made the right wing hit the ground first. $\endgroup$– TomMcWCommented Oct 12, 2017 at 17:52
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1$\begingroup$ Gotcha - I probably should have just noted it as related. aviation.stackexchange.com/questions/39020/… $\endgroup$– Russell BorogoveCommented Oct 12, 2017 at 20:01
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3$\begingroup$ In the case of UA232, the horizontal stabilizers had been damaged and there was a continuous tendency to turn right (that's from the report.) According to Wikipedia, fully asymmetric thrust only barely corrected this. That doesn't leave much margin for any other control actions. $\endgroup$– sdenhamCommented Oct 12, 2017 at 22:08
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1$\begingroup$ Q: So, what is your opinion on landing at Sioux City? A: It SUX. $\endgroup$– Robert ColumbiaCommented Oct 12, 2017 at 22:23
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2$\begingroup$ @RobertColumbia: Well, landing at Rapid City is KRAP. $\endgroup$– Fred LarsonCommented Oct 13, 2017 at 13:38
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1 Answer
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Some airliners have in fact landed more or less successfully using only engine power for control. The 2003 DHL attempted shootdown incident is an example.
A major difference between United 232 and Fullerton's landings you cite is that Fullerton was working for NASA testing a system designed specifically for the purpose of assisting pilots in controlling an aircraft with power alone. United 232 had no such system. See https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-041-DFRC.html
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2$\begingroup$ Apparently, I missed the point that F-15 had PCA system specifically built for differential thrust assistance. Thanks! $\endgroup$ Commented Oct 12, 2017 at 16:35