747 Technical / Cockpit Question for a Travel Book I'm Writing
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747 Technical / Cockpit Question for a Travel Book I'm Writing
Hi,
I wondered if there are any 747 pilots on here that might be able to help me. I'm trying to write a travel book, and the first journey had a lot of incidents that all stemmed from our PIA 747 (the journey was in 1994) being unable to retract the flaps after take off. The pilots had to dump a lot of fuel over the North Sea and return to Heathrow.
I thought it might make the description of this a bit more interesting if I wrote the intro from the pilot's perspective (on a very basic level). Therefore, I was wondering if any 747 pilots could help me with a couple of questions:
1. At what stage after take-off would the pilots have first tried to retract the flaps (or stage(s) of flaps)?
2. When and how would they have realised that there was a fault with the flaps. Would there be a master caution light or a hydraulic warning light etc?
3. When we landed, we burst 7 of the tyres on the undercarriage. Would there be any other hazards associated with that?
Many thanks indeed for any help!
I wondered if there are any 747 pilots on here that might be able to help me. I'm trying to write a travel book, and the first journey had a lot of incidents that all stemmed from our PIA 747 (the journey was in 1994) being unable to retract the flaps after take off. The pilots had to dump a lot of fuel over the North Sea and return to Heathrow.
I thought it might make the description of this a bit more interesting if I wrote the intro from the pilot's perspective (on a very basic level). Therefore, I was wondering if any 747 pilots could help me with a couple of questions:
1. At what stage after take-off would the pilots have first tried to retract the flaps (or stage(s) of flaps)?
2. When and how would they have realised that there was a fault with the flaps. Would there be a master caution light or a hydraulic warning light etc?
3. When we landed, we burst 7 of the tyres on the undercarriage. Would there be any other hazards associated with that?
Many thanks indeed for any help!
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1. Soon after you reach a safe altitude. you can start to retract your flaps to improve your climb performance. For a sea-level airport, the altitude is maybe 1000' AGL or even as low as 800' AGL. It all depends on the terrain.
2. There will be a caution message to warn the pilot if anything goes wrong. the leading flaps for 747 can be actuated with pneumatic power in normal mode and in electric power in secondary mode. For training edge flaps, it can be actuated with hydraulic power in normal mode and with electric power in secondary mode. The transition from normal mode to secondary mode is automatic.
Since there is a demand pump to support the main hydraulic pump, it is very unlikely to lose all hydraulic power for any system.
3. The bursting of 7 tires will significantly reduce your capability to stop the airplane, furthermore, those wheels spin at high speed with a loose thread that may damage piping or electric wires, thus disabling the airplane even more.
2. There will be a caution message to warn the pilot if anything goes wrong. the leading flaps for 747 can be actuated with pneumatic power in normal mode and in electric power in secondary mode. For training edge flaps, it can be actuated with hydraulic power in normal mode and with electric power in secondary mode. The transition from normal mode to secondary mode is automatic.
Since there is a demand pump to support the main hydraulic pump, it is very unlikely to lose all hydraulic power for any system.
3. The bursting of 7 tires will significantly reduce your capability to stop the airplane, furthermore, those wheels spin at high speed with a loose thread that may damage piping or electric wires, thus disabling the airplane even more.
Hello Rowan,
1. The altitude at which the flaps will be retracted can depend on a few factors. The aircraft will commonly climb to about 1000' above airfield elevation and then transition to a shallower climb as the flaps are retracted through all the stages to clean. 1000' is a typical altitude to start this process, however it may be delayed higher for other factors such as clearing a close in height requirement (obstacle or airspace) or for noise abatement.
2. It depends on what the problem actually was, and when the jet detected the problem. As soon as the 747-400 detects a problem with flaps, an appropriate message in amber will appear on the centre instrument panel (on the same "TV screen" as the engine instruments). There is a hierarchy of messages from MASTER WARNINGS (bad) to simple memos. A flap issue will generate a yellow alert message with a brief aural tone to get the pilot's attention. It would be accompanied by a MASTER CAUTION light. There are a number of possible problems the aircraft you were on had; from your description I would hazard a guess it was a FLAPS DRIVE problem. This is where one section of the flaps are mechanically stuck and the primary and secondary means of retracting/extending will not work. The rear flaps are divided into four sections and to preserve controllability, are linked symmetrically and will fail sympathetically, e.g. if the left inboard section locked, the right inboard section would lock as well. On climb out this would mean you will have that section stuck where it failed (symmetrically), the others sections work normally. You will dump fuel to reduce weight and therefore landing speed, set the flaps at their maximum landing setting (FLAP 30) and land. As you have less flap out, the checklist will direct the pilots to fly an approach speed that corresponds to FLAP25 approach speed + 20 knots......call it 25 knots faster than normal.
3. The tires bursting is a little unusual, even for a FLAPS DRIVE landing. Although landing faster, its not a huge deal and at maximum landing weight at Heathrow there is plenty of runway. Unless there were other circumstances it may have been over enthusiastic manual braking on the part of the handling pilot. As kuobin mentions, it may affect landing distance and can possibly further damage the aircraft, but not likely to offer any particular risk to passengers.
1. The altitude at which the flaps will be retracted can depend on a few factors. The aircraft will commonly climb to about 1000' above airfield elevation and then transition to a shallower climb as the flaps are retracted through all the stages to clean. 1000' is a typical altitude to start this process, however it may be delayed higher for other factors such as clearing a close in height requirement (obstacle or airspace) or for noise abatement.
2. It depends on what the problem actually was, and when the jet detected the problem. As soon as the 747-400 detects a problem with flaps, an appropriate message in amber will appear on the centre instrument panel (on the same "TV screen" as the engine instruments). There is a hierarchy of messages from MASTER WARNINGS (bad) to simple memos. A flap issue will generate a yellow alert message with a brief aural tone to get the pilot's attention. It would be accompanied by a MASTER CAUTION light. There are a number of possible problems the aircraft you were on had; from your description I would hazard a guess it was a FLAPS DRIVE problem. This is where one section of the flaps are mechanically stuck and the primary and secondary means of retracting/extending will not work. The rear flaps are divided into four sections and to preserve controllability, are linked symmetrically and will fail sympathetically, e.g. if the left inboard section locked, the right inboard section would lock as well. On climb out this would mean you will have that section stuck where it failed (symmetrically), the others sections work normally. You will dump fuel to reduce weight and therefore landing speed, set the flaps at their maximum landing setting (FLAP 30) and land. As you have less flap out, the checklist will direct the pilots to fly an approach speed that corresponds to FLAP25 approach speed + 20 knots......call it 25 knots faster than normal.
3. The tires bursting is a little unusual, even for a FLAPS DRIVE landing. Although landing faster, its not a huge deal and at maximum landing weight at Heathrow there is plenty of runway. Unless there were other circumstances it may have been over enthusiastic manual braking on the part of the handling pilot. As kuobin mentions, it may affect landing distance and can possibly further damage the aircraft, but not likely to offer any particular risk to passengers.
Here is a decent 747 systems groundschool.
It will help you understand how some of systems relevant to your story work and to use the correct nomenclature.
https://m.youtube.com/playlist?list=...FU0jiWbk_FDwcH
It will help you understand how some of systems relevant to your story work and to use the correct nomenclature.
https://m.youtube.com/playlist?list=...FU0jiWbk_FDwcH
