Fuel heat
Thread Starter
Join Date: Jul 2002
Location: Netherlands
Age: 71
Posts: 165
Likes: 0
Received 0 Likes
on
0 Posts
Fuel heat
I flew the B747-200/300 and later the B744 series, last flight was close to 10 Years ago so some things are getting faint.
We had a discussion last night about the fuel heat system of the P&W engines on the 200 series. We used it a lot on wintery nights, was a good issue to keep the F/E off the street as it needed constant attention in low OAT's
Once it was really cold and for some reason the F/E let his guard down, suddenly two of the Pratts started accelerating uncontrolled.
I was quick to pull back the levers and they responded and so we could avoid an engine overspeed. With heaters on they quickly recovered to normal ops.
Later with the GE CF6 on both the 300 and 400 series it was not needed any more. I completely forgot how this was solved on those heavenly good engines. (in 18000+ hours I never "lost" an engine.....I am forever grateful to GE for that design)
Is the heating done automatically or does the CF6 plumbing and control not require it?
We had a discussion last night about the fuel heat system of the P&W engines on the 200 series. We used it a lot on wintery nights, was a good issue to keep the F/E off the street as it needed constant attention in low OAT's
Once it was really cold and for some reason the F/E let his guard down, suddenly two of the Pratts started accelerating uncontrolled.
I was quick to pull back the levers and they responded and so we could avoid an engine overspeed. With heaters on they quickly recovered to normal ops.
Later with the GE CF6 on both the 300 and 400 series it was not needed any more. I completely forgot how this was solved on those heavenly good engines. (in 18000+ hours I never "lost" an engine.....I am forever grateful to GE for that design)
Is the heating done automatically or does the CF6 plumbing and control not require it?
Join Date: Aug 2006
Location: USA
Posts: 142
Likes: 0
Received 0 Likes
on
0 Posts
GE fuel routing
I've only flown one 74 with Prat power, god bless Miss Piggy. But, as I recall with GE's the fuel passes through a fuel oil heat exchanger. If the fuel/oil exchange shows low flow or clogged only then is heat applied to clear the ice blockage. A note in the handbook, basically said continue and monitor. I don't know if I ever saw this development in fifteen year of 200/300 operations.
Even several year ago, when FL temperatures across central/eastern Europe were extremely low, the whale has a hot wing. Don't think I've ever seen the fuel temperature ever approach with in plus ten of the fuel freeze point.
The procedure was always to speed up, maybe M.86 or a bit more or lower FL or both.
It would be interesting to hear some comments form operators of the newer higher out put engines from both Prat and GE on how the systems operate in real life.
Even several year ago, when FL temperatures across central/eastern Europe were extremely low, the whale has a hot wing. Don't think I've ever seen the fuel temperature ever approach with in plus ten of the fuel freeze point.
The procedure was always to speed up, maybe M.86 or a bit more or lower FL or both.
It would be interesting to hear some comments form operators of the newer higher out put engines from both Prat and GE on how the systems operate in real life.
Join Date: Apr 2008
Location: nowhere
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
I've only flown one 74 with Prat power, god bless Miss Piggy.
Even several year ago, when FL temperatures across central/eastern Europe were extremely low, the whale has a hot wing. Don't think I've ever seen the fuel temperature ever approach with in plus ten of the fuel freeze point.
The procedure was always to speed up, maybe M.86 or a bit more or lower FL or both.
Even several year ago, when FL temperatures across central/eastern Europe were extremely low, the whale has a hot wing. Don't think I've ever seen the fuel temperature ever approach with in plus ten of the fuel freeze point.
The procedure was always to speed up, maybe M.86 or a bit more or lower FL or both.
Sure would be nice if they used Jet A-1 in America.
The short answer is that all engine types on Boeing 747-400 - PW4000, CF6-80C2, and RB211-524G/H - (and subsequent engine/aircraft such as the 777) have automatic fuel heating via a fuel/oil heat exchanger. There is a note in the AFM to ensure the oil temperature is above some value (it varies a bit with engine type) before setting takeoff thrust. That ensures that there is sufficient heat in the FOHX to prevent fuel icing.
Note that it was the FOHX that was obstructed with ice on the BA 777/Trent that landed short at Heathrow
Note that it was the FOHX that was obstructed with ice on the BA 777/Trent that landed short at Heathrow
There is a note in the AFM to ensure the oil temperature is above some value (it varies a bit with engine type) before setting takeoff thrust. That ensures that there is sufficient heat in the FOHX to prevent fuel icing.
Join Date: May 2008
Location: Scotland
Age: 80
Posts: 451
Likes: 0
Received 0 Likes
on
0 Posts
All RB211 in 747's and Tristar had automatic fuel heat from the FCOC - fuel cooled oil cooler. JT9 had manually controlled fuel heat with switches on F/E panel. I was once slightly involved with an incident where the F/E on a 727 had the fuel heat selected on take off - the fuel into the engine overheated and on reducing power went sub idle causing all three generators to trip off - fortunately it was daylight and he managed to land with no further incident. On Pratts advice all 3 engines were replaced. Expensive error.
In our 744 FCOM there's one sentence in the engine fuel section that says engine oil heats the fuel in the heat exchanger. In the engine oil section there's one sentence that says the oil is cooled by the fuel in the heat exchanger. And that's how all that stuff works.
On the Seven Two there was a max fuel temp around 55c. At that point the fuel would not be a heat sink and you could cook the engine. Probably why Pratt suggested the engine change.
I've seen the other end. Minus 20/25 fuel. Everything nice and warmed up and when T/O thrust was set the oil temp dropped off the bottom of the scale. Pressures were still good at V1 so we keep going. Oil temp gradually came back into the green as we climbed.
On the Seven Two there was a max fuel temp around 55c. At that point the fuel would not be a heat sink and you could cook the engine. Probably why Pratt suggested the engine change.
I've seen the other end. Minus 20/25 fuel. Everything nice and warmed up and when T/O thrust was set the oil temp dropped off the bottom of the scale. Pressures were still good at V1 so we keep going. Oil temp gradually came back into the green as we climbed.
Join Date: Apr 2008
Location: nowhere
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
I was once slightly involved with an incident where the F/E on a 727 had the fuel heat selected on take off - the fuel into the engine overheated and on reducing power went sub idle causing all three generators to trip off - fortunately it was daylight and he managed to land with no further incident. On Pratts advice all 3 engines were replaced. Expensive error.
Bad news if left on.
Thread Starter
Join Date: Jul 2002
Location: Netherlands
Age: 71
Posts: 165
Likes: 0
Received 0 Likes
on
0 Posts
We sure did encounter enough low temps above a nightly Siberia, -76 was the lowest I ever saw in dec 1990 (one of my few written down "records").
I remember around -37 or -38 the low fuel temp wrng would pop up in the 744, but then it was already in a down cooling mode and You had to be careful it did not just keep on dropping. As most pilots we did not want to give up our sometimes difficult acquired level (huge time/dist separations used by the Russians), so all was left was to increase speed, I touched m.9 a few times, knowing the beast was certified (or tested I believe)till at least .92.
Later our company used a computer tool that had all the variables in and warned of a possible low fuel temp during prep. You could then decide upon taking extra fuel for speeding up.
Once during an extreme cold spell at high levels near Iceland we ran into problems with the fuel at the lowest possible allowed for that type of fuel. (that still had some 3 degr margin before actual start of freezing.
Already at max speed, we were trapped with planes below and above us, ATC (on HF) giving no help or solution. Later I heard that a lot of other planes were running into problems that night over icy Greenland.
I was close to calling a mayday and doing the NATL decompression manoeuvre to get lower.
OK, the problem will dissipate in future with the global warming, at which I can be blamed too with 18000 hrs on mainly 3 and 4 holers.....plus some three quarters of a million car kms...
I remember around -37 or -38 the low fuel temp wrng would pop up in the 744, but then it was already in a down cooling mode and You had to be careful it did not just keep on dropping. As most pilots we did not want to give up our sometimes difficult acquired level (huge time/dist separations used by the Russians), so all was left was to increase speed, I touched m.9 a few times, knowing the beast was certified (or tested I believe)till at least .92.
Later our company used a computer tool that had all the variables in and warned of a possible low fuel temp during prep. You could then decide upon taking extra fuel for speeding up.
Once during an extreme cold spell at high levels near Iceland we ran into problems with the fuel at the lowest possible allowed for that type of fuel. (that still had some 3 degr margin before actual start of freezing.
Already at max speed, we were trapped with planes below and above us, ATC (on HF) giving no help or solution. Later I heard that a lot of other planes were running into problems that night over icy Greenland.
I was close to calling a mayday and doing the NATL decompression manoeuvre to get lower.
OK, the problem will dissipate in future with the global warming, at which I can be blamed too with 18000 hrs on mainly 3 and 4 holers.....plus some three quarters of a million car kms...
Join Date: Jan 2006
Location: Ijatta
Posts: 435
Likes: 0
Received 0 Likes
on
0 Posts
When I used to fly the polar routes from DTW to HKG, the company would send a sample of our fuel to a lab to determine the actual fuel freeze point for that particular fuel load.
We usually got the results via ACARS within an hour or so of departure and would then enter the actual fuel freeze temperature into the FMS in order to overwrite the default value.
I don't recall ever having to speed up or change altitude due to fuel temperature issues, but I may have just been lucky.
We usually got the results via ACARS within an hour or so of departure and would then enter the actual fuel freeze temperature into the FMS in order to overwrite the default value.
I don't recall ever having to speed up or change altitude due to fuel temperature issues, but I may have just been lucky.
Even with automatic fuel heat in a RR powered B747-200, encountering a very cold air mass could still mean that the temperature of the fuel in the tanks could fall to its limiting temperature.
The night of 19 February 1993 was an extremely cold night over the North Atlantic. Whilst cruising on the NA track system, operating MCO to LGW, in a RR powered B747-236, we encountered a SAT of -72°C.
Speeding up had no visible effect on the ever decreasing tank temperature, and with no lower level available from ATC, we eventually had to declare an emergency, turn off track and establish a parallel offset track and then descend to FL 320 in search of warmer air.
By the time we left oceanic airspace that night we had heard several other aircraft also offset from the track system in order to descend in to warmer air.
The night of 19 February 1993 was an extremely cold night over the North Atlantic. Whilst cruising on the NA track system, operating MCO to LGW, in a RR powered B747-236, we encountered a SAT of -72°C.
Speeding up had no visible effect on the ever decreasing tank temperature, and with no lower level available from ATC, we eventually had to declare an emergency, turn off track and establish a parallel offset track and then descend to FL 320 in search of warmer air.
By the time we left oceanic airspace that night we had heard several other aircraft also offset from the track system in order to descend in to warmer air.
Thread Starter
Join Date: Jul 2002
Location: Netherlands
Age: 71
Posts: 165
Likes: 0
Received 0 Likes
on
0 Posts
wanabee, it took quite some time before the values started getting real low.
In the beginning the "warm" fuel quantity is big but as the flight progresses, reducing fuel quantities receive the same cold "energy" and thus temps are falling quicker.
Long flights into very long winter nights in the northern hemisphere gets the plane eventually cold soaked.
If I remember correctly problems started after 5-7 hours into a typical flight from AMS-NRT or the likes.
In the beginning the "warm" fuel quantity is big but as the flight progresses, reducing fuel quantities receive the same cold "energy" and thus temps are falling quicker.
Long flights into very long winter nights in the northern hemisphere gets the plane eventually cold soaked.
If I remember correctly problems started after 5-7 hours into a typical flight from AMS-NRT or the likes.
Join Date: Jan 2006
Location: Ijatta
Posts: 435
Likes: 0
Received 0 Likes
on
0 Posts
Double Back,
We were, no doubt, well out of the low temperature regions by the time our fuel load was low enough to make a difference. Probably over Mongolia heading south toward China.
On the HKG to DTW return leg, I don't think we were flight planned via the polar routes.
We were, no doubt, well out of the low temperature regions by the time our fuel load was low enough to make a difference. Probably over Mongolia heading south toward China.
On the HKG to DTW return leg, I don't think we were flight planned via the polar routes.
Thread Starter
Join Date: Jul 2002
Location: Netherlands
Age: 71
Posts: 165
Likes: 0
Received 0 Likes
on
0 Posts
On one (daytime) return flight in winter in that crisp cold air we questioned the controller of Mirny (that place with those enormous large surface diamond mines https://en.wikipedia.org/wiki/Mir_mine ) what the local temp was at the moment. He said -35, where upon we woooowed in a reply from our comfortable cockpit, sipping coffee. Then he kinda shrugged and said that they thought it was real cold when temps started getting below -50....
read this one about living in Yakutsk, a "bit" further to the NE: Yakutsk: Journey to the coldest city on earth | Europe | Travel | The Independent
read this one about living in Yakutsk, a "bit" further to the NE: Yakutsk: Journey to the coldest city on earth | Europe | Travel | The Independent
