I know this topic has been talked to death, but I was just watching about the British Airways flight that crashed at Heathrow, b/c of ice restricting the fuel flow in the heat exchanger in the 777, and then again in the US on a Delta flight b/c of water in the fuel. Is there a way to implement a system failure in an upcoming update where if your fuel gets too cold it gels or freezes and causes the engines to roll back? Only reason I ask is that I'm flying the 787 right now and my fuel temps are -65c. I don't even know if this is doable, but I wonder if it could be implemented with the addition of an extra fuel warming switch for say the tanks. Kinda like the same principle of de-iceing on an a/c. Any thoughts?

fuel flow in the heat exchanger in the 777, and then again in the US on a Delta flight b/c of water in the fuel. Is there a way to implement a system failure in an upcoming update where if your fuel gets too cold it gels or freezes and causes the engines to roll back?

 

At least on the MD-11, if the fuel gets too cold, the engine(s) will flameout/fail. I think the failure is already implemented in other products.

 

Only reason I ask is that I'm flying the 787 right now and my fuel temps are -65c. I don't even know if this is doable, but I wonder if it could be implemented with the addition of an extra fuel warming switch for say the tanks. Kinda like the same principle of de-iceing on an a/c. Any thoughts?

 

I don't know of any fuel type that freezes at -65. I think the lowest is -50. I would descend/climb to a warmer altitude and try to get out of that weather.

 

I think it also has to do with the system programming behind the panel. Some aircraft may not have the same level of programming that others have.

I don't know of any fuel type that freezes at -65. I think the lowest is -50. I would descend/climb to a warmer altitude and try to get out of that weather.

 

Well I'm doing a transatlantic flight from EGLL to KBOS in a 787. at FL380. I tend to get the best fuel consumption at that FL, if i descend to say FL300 I end up burning more fuel. Just trying to increase the realism of FSX and some of my not so pay a/c (the free ones :lol: ). I have alot of payware and freeware a/c and haven't had any, where the fuel freezes on me and rolls the engines back. Don't even know at what temp Jet-A freezes at. Just a thought I had.

In a 787? I wouldn't worry about to cold fuel, but instead prepare a fire extinguisher.

 

But back to topic. Well, I am not an expert, but for instance in the MD-11, the fuel system controller starts to transfere fuel arround to creat heat and exchange warmer fuel from the center tank with colder fuel in the wing tanks. Other aircraft may have similar procedures to keep the fuel warm. If it doesn't help you have to descent.

 

There is absolutly none advantage of cruising at FL380 instead of FL340, when your fuel freezes.

 

And I don't asume fuel could ever get that cold as -65°C. In the standart atmosphere the coldest temperature a modern jet could theoretically fly through is -56°C. Above the altitude it has -56°C temperatures climb again.

But even if it had -56°C, which is our Outside Air Temperature (OAT), I don't expect that your fuel will reach -56°C even on a long flight. The reason for that is quit simple. As you move through the air your plane get's warmed up by friction. Your Total Air Temperature (TAT) is higher (e.g.: -50°C) and your fuel will only cool down to -50°C, not to -56°C.

 

The PMDG MD-11 simulates this, and I expect the NGX does that too, but I don't know about other developers.

 

If you know you will fly trough low temperatures (as you can see in the briefing you make before the flight) you will have to consider if it's worth to tanker JET-A, JET-B, or whatever. Else you might want to change your route or fly below optimal cruise altitude. It's always better to burn more fuel than to burn no fuel.

 

Best regards,

 

Jonathan

The affected aircraft were modified after the BA accident to ensure ice crystals couldn't accumulate around the fuel filters, so it shouldn't be a problem in future. In theory at least. The particular condition was a very unusual combination of circumstances. The ice accumulated throughout the fuel system and was suddenly released into the filters when power was increased during the approach. I'm sure PMDG could add this to the simulation, if they haven't already. Just as long as it doesn't delay release...

I don't even know if this is doable, but I wonder if it could be implemented with the addition of an extra fuel warming switch for say the tanks. Kinda like the same principle of de-iceing on an a/c. Any thoughts?

The 777 has a similar system like the G5/550. It's called the heated fuel return system(Rolls Royce engines). The fuel routes through a fuel cooled oil cooler, which heats the fuel up to 50C(G5 number). The fuel then routes to the engines. Prior to entering the fuel control, a valve diverts excess fuel back to the fuel tanks. On the Gulfstreams, the valve opens at a fuel temp of 0C and closes above 10C. The system also shutdowns during high fuel flow, open crossfeed valves, fire handle pulled, etc. The min fuel temp in the Gulfstream -37C. Even though we have this system, we use prist when ever we refuel.

 

The word from the 777 is this. During descent with throttles at idle, the HFRS was sending the warm fuel back to the tanks. During this time, the low fuel flow to the engines cooled quickly. Water in the fuel began to ice up and cause restriction at the engines. This is why the engines would not respond above idle. After this incident, Gulstream recommended that we turn the HFRS off during descent. This prevents the warm fuel from diverting back to the fuel tanks. I've been told that this wouldn't happen on the 5/550, but it's a CYA thing for Gulfstream. Like stated above, the fuel wouldn't get that cold. We normally cruise from FL400 up to FL470, and certified up to FL510. Never have I seen the fuel get below -15 on our longest leg(13 hours). The HFRS mainly warms the fuel in the outboard section of the tanks. Our QRH does recommend descending if the temp reaches minimum temp with the HFRS failed.

Hey Rick I've always wondered, when you awesome gulf stream and global express pilotsare ddoing those long 13 hour flights do you need to carry additional pilots like the airliners?

 

And I don't asume fuel could ever get that cold as -65°C. In the standart atmosphere the coldest temperature a modern jet could theoretically fly through is -56°C. Above the altitude it has -56°C temperatures climb again.

 

Jonathan

 

It can get MUCH colder than that in r/w conditions, especially over tropical latitudes, due to the fact that the tropopause (the boundary between the troposphere and stratosphere) is much higher over the tropics. The atmospheric temperature keeps dropping with height until reaching the tropopause, at which point it levels off, or even starts climbing again. Over northern latitudes, the tropopause in winter can be in the low to mid 30, 000 foot range, while over the tropics it can be as high as 55,000 to 60,000 feet.

 

I spent a few months as a flight mechanic on a Gulfstream IV based in Africa. We flew north to the UK a couple of times per month. I remember one flight in particular, where the temperature at 43000 feet over Kano, Nigeria was -75C! Interestingly, the surface temp at Kano, directly below, was +36 at the same time.

 

One problem with many non-PMDG-quality FSX add-ons (that display fuel temp) is that the fuel immediately assumes the temperature of the surrounding atmosphere as the aircraft climbs. This is NOT what happens in the real world. If the fuel was loaded in a warm location, it can take hours for it to chill down to the TAT at altitude.

 

That was the case in the above flight, where we had taken a full load of fuel at Lagos, which was about +29C when it went in the tanks. An hour later we were flying through the region with a static OAT of -75C, but the fuel temperature hadn't yet even dropped below 0C.

 

The NGX is one of the few FSX aircraft I have seen that accurately simulates the actual rate at which fuel cools with time.

Hey Rick I've always wondered, when you awesome gulf stream and global express pilotsare ddoing those long 13 hour flights do you need to carry additional pilots like the airliners?

Those long 13 hour flights are rare for us and we would augment. Normally we use one crew to complete our flights. If the boss has to get there in a hurry, we will preposition a crew. For example, if the boss needs to get to Japan ASAP, we will pre-position a crew to Hawaii. One crew flys out to Hawaii, and the pre-positioned continues on to Japan after refueling. This is the quickest way to get to Asia without having to stop the jet due to crew-rest. In flight crew rest facilities takes up valuable space.

Just wanting a more realistic FSX, here is a pic of fuel temps in my current flight from PAJN to KMIA. And it is Abacus, so maybe they just don't care about getting it right. -50c, first time I have ever noticed the fuel was the post i made above. Never even paid attention to temps, until the video i saw. Now I'm like...hhmmmmm......

 

You can see that your TAT is -27°C and that's the temperature the fuel should reach after a long time, not -50°C.

In cruise flight and increase in your speed will raise your fuel temp do to the increased friction and prevent the fuel from freezing. At least in the real world.

At the very least there is a warning that pops up on the EICAS when fuel temp is low to alert the crew, this should surely be easy to simulate?

In a 787? I wouldn't worry about to cold fuel, but instead prepare a fire extinguisher.

 

This is the correct answer. If the fuel gets too cold the battery catches on fire to warm it back up.