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Dumping Fuel, 727

Thu Feb 08, 2001 6:07 am

Concerning a 727 dumping fuel on approach: I'm editing a novel where the author has this 727 twenty minutes out from Missoula, MT after departing Salt Lake City. It's struck by lightning, damaging the hydraulics so the crew must lower the gear mechanically. Flaps and spoilers are apparently inoperative.

Also, this author has the crew dumping fuel. Any input would be appreciated so we can get this right.
 
JETPILOT
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Joined: Tue May 18, 1999 6:40 am

RE: Dumping Fuel, 727

Thu Feb 08, 2001 8:20 am

There is only reason I can think of for the plane to dump fuel is that on a no flap landing the approach speed is Vref plus 60.

In order to meet the runway requirments the pilot may elect to dump fuel.

Lightning will not damage the hydraulics since the A system which operates the gear is pressurized by engine driven pumps on engines 1 and 2.

The flaps can be extended electricly or hydraulicly in case of a failure of either.

The spoilers are powered by both A and B systems so some spoilers will work. The inboard flight spoilers are powered by B system. the outboard spoilers will still work if system A is operable.

There is no way to lose all hydraulics on the 727 unless both A and B system integrity are lost.

I could think of a better scenario that would be totally realistic if you want.

JET
 
Guest

RE: Dumping Fuel, 727

Thu Feb 08, 2001 1:28 pm

Would welcome your better scenario. Thanks for your time and effort with this.
 
Guest

RE: Dumping Fuel, 727

Thu Feb 08, 2001 1:37 pm

Your hydraulic info is especially helpful in explaining to this author why we might need to revise the chain of events. Novel's email is cotton@noveledit.com.
 
WorldTraveller
Posts: 594
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RE: Dumping Fuel, 727

Fri Feb 09, 2001 7:33 am

Pardon my ignorance, but I was under the impression that the B727 cannot dump fuel!?

?

Best regards
the WorldTraveller
 
JETPILOT
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RE: Dumping Fuel, 727

Fri Feb 09, 2001 8:27 am

It can.

JET
 
Dalmd88
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RE: Dumping Fuel, 727

Fri Feb 09, 2001 9:48 am

I know from experience it can dump fuel, even parked in a hanger. I left my tool box parked under the wingtip one day. I came in the next night and every thing was soaked. Seams that while fueling the plane someone accidently opened the dump valves on that side.
 
JETPILOT
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RE: Dumping Fuel, 727

Fri Feb 09, 2001 12:27 pm

It sounds more likely that the fuel vented overboard through the tank vent.

I can't imagine someone opening the dump valves and dump nozzles and turning the boost pumps on. To many things need to be done before fuel can be dumped.

But the VTO fails all the time.

JET
 
DE727UPS
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RE: Dumping Fuel, 727

Sun Feb 11, 2001 10:54 am

If you got hit by lightning you would be more likely to have electrical problems....at least in theory....than hydraulic problems. You could make it so that lightning burned holes in both the A and B hydraulic systems but if you want to dump fuel you need at least the essential AC buss operating.....and if you had a total electrical failure....you wouldn't have this so you wouldn't be able to dump. You could run the problem so you lose both system A and B hydraulics.....and lose all but standby electrical power, which gives you minimal stuff for 30 minutes.....then have the flight engineer be the hero by getting you essential AC power back by the rarely known "boot strap" method of holding the field relay switches up......then with only essential power you could dump through only one dump nozzle.

Hope that isn't too technical.....e-mail me if I can help you more. I could look in my systems manual to get more exact information.
 
JETPILOT
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Joined: Tue May 18, 1999 6:40 am

RE: Dumping Fuel, 727

Sun Feb 11, 2001 11:32 am

I don't know if you knew this but the battery on the 727 will only supply a max of 25 minutes of battery power when in STBY. The STBY horizon, which must be reliable for a minimum of 30 minutes is still reliable for 5 minutes while it is spooling down.

I never heard of holding the filed relays closed like that.

You can dump through one dump nozzle and only tank #2 when operating with essential.

A good secenario would be to fail a seal on the elevator PCU dumping both A and B overboard. Control wouldn't be a problem beacuse you have manual reversion.

The scenario could inlude dumping fuel to get into a 3000 ft field the 727 wouldn't normally make. Maybe a flap 40 landing which would have to utilize airbrakes.

A lightning strike scenario isn't practical because the electricity travels through the skin of the plane and doesn't really affect anything.

Would you have reversers with loss of all hydraulics?

I am not sure. I think they are hydraulic.

JET

JET
 
Victor Hotel
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RE: Dumping Fuel, 727

Sun Feb 11, 2001 12:54 pm

When people nread the novel though are they going to be really critical about it. What I am saying is not everyone has this kind of understanding of a/c systems that most people here do, so wouldn't people just accept what happens in the book, unless somthing is obviously not going to happen. The majority of people though are probably not going to know the working systems of the 727, and are buying the book for a good read.
VH
 
DE727UPS
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RE: Dumping Fuel, 727

Sun Feb 11, 2001 1:01 pm

Most of our 727's have the Rolls Royce Tay conversion and have bucket type reversers rather than cascade vane type. We need hydraulics to operated them but there is an accumulator that should make them work even if you lost system A. I like your idea of a 3000' runway....make them do a GPS approach because the airport has no navaids. Some kid in the back has a hand held GPS receiver they use.
 
JT8DJET
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RE: Dumping Fuel, 727

Sun Feb 11, 2001 1:21 pm

The T/R's on a JT8D (-17 and prior) powered 727 use 13th stage bleed air.

 
jjbiv
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RE: Dumping Fuel, 727

Sun Feb 11, 2001 2:40 pm

How reliable is a GPS operating inside an aluminum tube without an external antenna? Can't say I've ever tried it, but I'm curious now  Smile/happy/getting dizzy
 
EssentialPowr
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RE: Dumping Fuel, 727

Sun Feb 11, 2001 2:47 pm

Great discussion, couldn't resist...

My book says that, on EssentialPowr, you've got the left dump valve out of tank #2, left dump nozzle, 2 pumps in #2, with about 300lbs/min/pump...You guys probably smoked the classic oral question, "...what is the max dump rate on standby power?"

Long live 3-1-2...
 
XFSUgimpLB41X
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RE: Jjbiv

Sun Feb 11, 2001 2:57 pm

The GPS will be reliable as long as the put it in the windows of hte cockpit...as long as it has a clear shot of the sky it will work quite nicely. I own a Garmin GPS Pilot III.... its really cool...and you would definitely be able to find your way around were something to really mess up on the airplane.
Chicks dig winglets.
 
JETPILOT
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RE: Dumping Fuel, 727

Sun Feb 11, 2001 4:34 pm

That's a classic qusetion. But if you understand the plane you'll never answer it incorrectly.

But the right way to answer the question is to ask the examiner weather you have overboost pumps in tank number 2. The 727 ADV came with those pumps cabable of 300 PPM each. But the lowly 200/100 only has 200 PPM pumps. The overboost pumps allow fuel crossfeeding from tank #2 to engines 1 and 3 with the boos pumps on in tank #1 and #3 during takeoff in the ADV. On the 100/200 you must take off in tank to engine configuration.

There's an easy way to remeber which pumps you have on ESS PWR. They called the RALF pumps. The Right Aft, and the Left Foward. You can never get through a 727 oral without them asking that.

The other pumps from left to right are the 13,21,23 pumps. AC generator bus 1 powers #1 pump and #2 by the AC#3 bus. In tank #2 the left aft pump is powered by AC bus #2, and the right foward pump is powered by AC bus #1. In tank #3 the left pump is powered with AC bus #2 and the right pump is powered by AC bus #3.

JET
 
JG
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RE: DALMD88 Et Al

Sat Feb 17, 2001 1:28 am

DALMD88- Just two cents worth. Having had the pleasure of actually dumping fuel in a 727 I must say that not just your tools would be soaked... I venture to say the whole hangar would be soaked and talked about by everyone from the earlier shift.  Smile

Additionally, my understanding of overriding fuel boost pumps was that they operate at a higher output pressure not a higher volume. The rule of thumb for dump rate determination was 300 ppm /pump for all versions. No big deal. Only a concern if you are on fire... just remember to turn them off, lest you make a wick leading to your parking spot.

Regards,
JG

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