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How Long It Takes To Fully Power 747 Classic?  
User currently online747400sp From United States of America, joined Aug 2003, 3479 posts, RR: 2
Posted (5 years 8 months 4 weeks 15 hours ago) and read 4924 times:

I was reading a trend on the anniversary of the Boeing 747, and some body stated that it took 15 to 20 min to start a 747 100 they was on. That seem a little long, so I wonder, how long do it take to fully start up a 747 classic? I know on a classic you have to start each engine one at a time, instead of two at a time like on a 744 or A380.

9 replies: All unread, jump to last
 
User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 1, posted (5 years 8 months 4 weeks 14 hours ago) and read 4908 times:

If all goes well and there are no interruptions it takes about 10 to 15 minutes from the beginning of the before start checklist to the end of the after start checklist. The two biggest variables are if we can start during the push or if we have to wait until brakes are set, and how quickly the engines spool up. Each engine typically takes about 90 sec from the beginning of the start until a stabilized idle is achieved.


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User currently offlineDocLightning From United States of America, joined Nov 2005, 19371 posts, RR: 58
Reply 2, posted (5 years 8 months 4 weeks 7 hours ago) and read 4806 times:



Quoting Lowrider (Reply 1):
If all goes well and there are no interruptions it takes about 10 to 15 minutes from the beginning of the before start checklist to the end of the after start checklist. The two biggest variables are if we can start during the push or if we have to wait until brakes are set, and how quickly the engines spool up. Each engine typically takes about 90 sec from the beginning of the start until a stabilized idle is achieved.

Fascinating. Suppose it was an emergency and you needed to go NOW (war breaks out or something equally improbable). How fast could you manage to go from a cold plane to T/O thrust?

How about on the -400?


User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 3, posted (5 years 8 months 4 weeks 7 hours ago) and read 4796 times:



Quoting 747400sp (Thread starter):
That seem a little long, so I wonder, how long do it take to fully start up a 747 classic?

First of all, the INS (Delco or Litton) take upwards of 10 minutes to align on the classic. The IRS on the 400 takes about 7 minutes to align. During that time, the aircraft can't be moved so you're stuck there. Once the gyro platforms are aligned, then it's just a matter of engine start. If you could start in the stand and taxi out without having to worry about push back, then it's about 5-6 minutes till you are ready to taxi. If you have to push back and can't start during the pushback, then add another 3-5 minutes.

So, you can see it's not a quick process at all.


User currently offlineFr8mech From United States of America, joined Sep 2005, 5330 posts, RR: 14
Reply 4, posted (5 years 8 months 4 weeks 5 hours ago) and read 4751 times:



Quoting Lowrider (Reply 1):
beginning of the before start checklist to the end of the after start checklist

Checklist???? We don't need no stinking checklist!!  Smile

You can get one going in 10 minutes, if you start the engines while the INS is counting down.

You're really limited by the INS.

From a dark cockpit:

-INS to NAV, we're moving fast now, no need to stop at ALIGN
-While waiting for the prompts, get the battery online and open the APU door. About 45 - 60 secs.
-Start APU. While the APU is starting (up 90 secs), you can enter your position into the INS. Don't worry, the INS countdown has begun.
--Stable APU? Electric and air. Radio masters, if equipped. Fuel pumps and #4 hydraulic pump.
-No time to waste, you're about 3 minutes into a 10 minutes countdown. Your panel should be configured for start (if you had a half-assed competent F/E).
-Air up? Turning #4. This is not where to cut time or it can cost you. Wait for at least 20%. Fuel in, light off, starter out at 50%. You will know if you're going hot by now. Move on to the next engine. Repeat the exercise 3 times. The F/E is keeping track of the running engines.
-Wait for the INS to fully countdown and go into NAV before swapping power. You can screw it up with a power swap during align.
-Taxi away, swap power, secure the APU and hope you can fly the thing without a programmed INS, assuming you have fuel in the right places.

A couple of competent, experienced folks can do it in 10 minutes.

Quoting DocLightning (Reply 2):
Fascinating. Suppose it was an emergency and you needed to go NOW (war breaks out or something equally improbable). How fast could you manage to go from a cold plane to T/O thrust?

On a classic, you don't buy a bunch of time from not aligning the INS. Not real sure about the -400. I do know that the 2 engined aircraft can be moving in under 5 minutes, but you will not have IRS (inertial reference system). I wouldn't be too keen on going without that. Too many aircraft systems depend on it for information.



When seconds count...the police are minutes away. Never leave your cave without your club.
User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 5, posted (5 years 8 months 4 weeks 4 hours ago) and read 4716 times:



Quoting Fr8mech (Reply 4):
A couple of competent, experienced folks can do it in 10 minutes.

With that NASCAR style start, I suppose you are right, but the fastest I have ever seen one go from cold and dark to ready to taxi is about 45 min. This does, of course, include things like weight and balance calculations, performance calculations, preflighting, walking the freight, and programming a relatively short, simple flight plan into the INS's.

Quoting DocLightning (Reply 2):
How fast could you manage to go from a cold plane to T/O thrust?

In that scenerio, I would say you are probably not going to make it to the runway. How much bigger a target could you ask for? But if you followed the above start procedure and either had your data pre calculated or just used a SWAG, I would thing you could be wheels up in 15 to 18 minutes, if your taxi wasn't too long.



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User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2543 posts, RR: 25
Reply 6, posted (5 years 8 months 4 weeks 2 hours ago) and read 4676 times:



Quoting Lowrider (Reply 1):
Each engine typically takes about 90 sec from the beginning of the start until a stabilized idle is achieved.

That sounds rather long. A JT9D-7 takes about 60 seconds to get to ground idle, a CF6-50 45 seconds or so. I've seen 4 CF6's started in quick succession, with the next engine start commencing as soon as EGT had peaked on the previous one, taking about 3 minutes total.

A Boeing test pilot I met a few years ago said that two engines could be started at once if necessary on th e747 Classic. They had checked it out for the military version (E-4). Easier with the GE engine's latched start switches, less easy with the manually held switches usually found on the PW version. He tried it in our P&W engined sim, just to see if it worked (it did). Of course the sim models a perfectly performing new APU.

This is all rather incidental, because as PhilSquares and others have said, the critical path is aligning the INS.

Quoting DocLightning (Reply 2):
Fascinating. Suppose it was an emergency and you needed to go NOW (war breaks out or something equally improbable). How fast could you manage to go from a cold plane to T/O thrust?

Without basic INS alignment you have no primary attitude or heading information, just the standby ADI and magnetic compasses. Probably no autopilot either as a result. You could stop the alignment early as soon as the ADI was erect and the HSI showed correct heading, switching the INS to attitude only. It wouldn't save a lot of time really.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 7, posted (5 years 8 months 4 weeks 2 hours ago) and read 4664 times:



Quoting Jetlagged (Reply 6):
That sounds rather long.

Perhaps, but it is what I have seen, the sequence usually goes:
From moving the swith to gnd start to max motoring 20 to 40 sec
From light off to stable idle (not starter cut out) 45 to 60 sec
So anywhere from 65 to 100 sec. Both times are entirely within the normal range. It seems that they starts are usually closer to the 100 sec mark than the 65 mark though. Maybe our APUs and starters are just older and more worn than yours though.



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User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 8, posted (5 years 8 months 3 weeks 6 days 23 hours ago) and read 4582 times:



Quoting Jetlagged (Reply 6):
Without basic INS alignment you have no primary attitude or heading information, just the standby ADI and magnetic compasses. Probably no autopilot either as a result.

Absolutely correct, no autopilot, no yaw damper. No nav capability since the RMI/HSI will not be working. There are a host of things you won't have.


User currently offlineFr8mech From United States of America, joined Sep 2005, 5330 posts, RR: 14
Reply 9, posted (5 years 8 months 3 weeks 6 days 21 hours ago) and read 4518 times:



Quoting Jetlagged (Reply 6):
Without basic INS alignment you have no primary attitude or heading information

That why skipping INS alignment in any scenario really doesn't buy you a thing, unless you want to fight that monster through the whole flight.

You can do dark to block in 10 minutes, but you will be skipping programming, briefing and checklists.



When seconds count...the police are minutes away. Never leave your cave without your club.
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