Timeline for Controlling jet engine thrust on airliners
Current License: CC BY-SA 3.0
12 events
| when toggle format | what | by | license | comment | |
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| Nov 18, 2016 at 4:27 | comment | added | Terry | @DeltaLima The airline I was flying for had a policy of normal landings at 30 degrees flaps. They allowed 40 for short field operations, and the sim demonstration was done, as I remember, at that setting. | |
| Nov 17, 2016 at 23:58 | comment | added | DeltaLima♦ | Your comments triggered me to do some research into the 727. Even at 2000ft per minute in landing config, 1500 feet descent while spooling up is still at least 45 seconds. That is too long for flight idle. What I found is that the 727-200 had excessive drag at flaps 40, and combined with the slow spool of the engines this led to several accidents. For that reason some airlines had a 1500ft stabilised approach criterion for the 727 fleet, others prohibited the use of flaps 40. | |
| Nov 17, 2016 at 21:34 | comment | added | Terry | @TomMcW No FADEC on the 727-100 or the 747-100/200. I know that when the 727 first flew, there was an engine surge problem, but I never experienced such. Perhaps that was because we were taught to advance the power levers slowly, and never to slam them forward. My guess now is that we typically took around 3 seconds to move the thrust lever from the idle position to the max thrust position. | |
| Nov 17, 2016 at 21:16 | vote | accept | RoboKaren | ||
| Nov 17, 2016 at 21:09 | comment | added | Terry | @RoboKaren Perhaps a better way to say it would be that flight idle was a greater percentage of the rpm range on the 747 than it was on the 727, but I'm really not an engineer. Also, I think the engine bypass ratio was higher on the 747. Also, I think the different wing had a lot to do with it. That, plus the 727 would develop a higher sink rate. With the 727 you could come down and slow down at the same time. With the 747 you could come down or slow down, but not at the same time. | |
| Nov 17, 2016 at 20:28 | history | edited | Terry | CC BY-SA 3.0 |
changed 1500 feet to hundreds of feet
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| Nov 17, 2016 at 20:22 | comment | added | Terry | @DeltaLima I actually meant 1500, and try as I might in rethinking what I wrote, that's the figure that sticks in my mind. Now, given the fact that it's been 26 years since I flew the 727 and that at age 77 dementia is probably setting in, I could be incorrect. I am, however, totally confident in saying that it was hundreds of feet, and I have edited my answer accordingly. Given a descent rate in excess of 2000 fpm and no meaningful power until the last part of the spool up, the point of the demonstration was that you didn't want to get into this condition anywhere close to the ground. | |
| Nov 17, 2016 at 19:32 | comment | added | TomMcW | When going from idle to full power on the 727 was there a risk of surging? (I'm assuming 727 did not have fadec) If so, how did you prevent it? | |
| Nov 17, 2016 at 18:25 | comment | added | DeltaLima♦ | I assume you mean 150 feet instead of 1500 feet. | |
| Nov 17, 2016 at 16:53 | comment | added | RoboKaren | Great answer! Can you explain in more detail why the 747 was more responsive? Was it that flight idle was simply at a higher rpm? | |
| Nov 17, 2016 at 0:03 | history | edited | Terry | CC BY-SA 3.0 |
added 1 character in body
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| Nov 16, 2016 at 21:29 | history | answered | Terry | CC BY-SA 3.0 |