Breaking News - Air India 171 to London Gatwick crashes in Ahmedabad - 240+ Souls

[WallFlowerActive]

There are many ways a tank could be contaminated that only affected that plane. If they used trucks it could be biocide used to clean the truck that wasn’t cleaned out well, if there was water in previous fuel loads there could be algae growing in the tank that partially blocked the fuel lines, there could have been something left in the fuel tank that blocked the fuel lines. There are any number of ways that fuel could have caused the engines to not produce power.

At a busy airport, how many times a day would that tanker truck be used?

[WallFlowerActive]

 If they used trucks 

Shrugs…

Ahmedabad Airport uses aviation fuel hydrants?

My old ford diesel has a water in fuel filter alarm.  

So.  How do you get contamination in the fuel where the engine stars, taxis with in acceptable performance to the pilots.  No fuel system alarms?  But contamination so bad the jet crashes a few seconds after liftoff?

[BeyondKnowledge]

Shrugs…

Ahmedabad Airport uses an aviation fuel hydrants?

My old ford diesel has a water in fuel filter alarm.  

So.  How do you get contamination in the fuel where the engine stars, taxis with in acceptable performance to the pilots.  No fuel system alarms?  But contamination so bad the jet crashes a few seconds after liftoff?

That is easy. The contamination was not significant enough to clog up whatever it did until the flow was greatly increased by actual takeoff settings instead of start and idle or the volume of fuel through the clog area had not been sufficien to build the clog yet. 

Also, the contaminant could have come from the hose or a slug of water or other fuel additive or contaminant from the underground distribution system. It has happened before.

[Zaphod58]

Shrugs…

Ahmedabad Airport uses aviation fuel hydrants?

My old ford diesel has a water in fuel filter alarm.  

So.  How do you get contamination in the fuel where the engine stars, taxis with in acceptable performance to the pilots.  No fuel system alarms?  But contamination so bad the jet crashes a few seconds after liftoff?

Honolulu used hydrants too, but we refueled from trucks sometimes.

Your Ford alarm isn’t going to go off if algae or something else is in the fuel.

 That’s sort of the point. Contamination generally doesn’t restrict low level fuel flow, such as idling and taxiing. When you put a higher load on the system and there’s more fuel flow, something can break loose and block fuel lines. That results in reduced power, possibly to the point you can no longer generate enough lift to remain airborne.

[WallFlowerActive]

That is easy. The contamination was not significant enough to clog up whatever it did until the flow was greatly increased by actual takeoff settings instead of start and idle or the volume of fuel through the clog area had not been sufficien to build the clog yet. 

Also, the contaminant could have come from the hose or a slug of water or other fuel additive or contaminant from the underground distribution system. It has happened before.

I’m totally ignorant.  But if I designed the system. It would be filtered, then injected to the engines.  The fuel pumps would pump a maximum amount of fuel at all times.  After the fuel filters, I would have a regulator that would feed the excess fuel the engines didn’t need back to the fuel tank.  

I think air intake to fuel is a big deal in aviation.  Wouldn’t that be one of the warnings.  Even on start up testing and taxing, checking to make sure the air to fuel ratio was within spec.  I would think contamination would throw that off.

[BeyondKnowledge]

I’m totally ignorant.  But if I designed the system. It would be filtered, then injected to the engines.  The fuel pumps would pump a maximum amount of fuel at all times.  After the fuel filters, I would have a regulator that would feed the excess fuel the engines didn’t need back to the fuel tank.  

I think air intake to fuel is a big deal in aviation.  Wouldn’t that be one of the warnings.  Even on start up testing and taxing, checking to make sure the air to fuel ratio was within spec.  I would think contamination would throw that off.

That design would be good on the ground but quite heavy in the air. Far better to keep the fuel clean before puting it into the aircraft but that doesn't always work because people are involved in the system. Mistakes can be made in fuel storage system design that doesn't show up for many years. People don't always follow established procedures by mistake or just being tired. 

There are many factors that we just don't know about yet. Crash reports sometimes take years to finish.

[WallFlowerActive]

  Contamination generally doesn’t restrict low level fuel flow, such as idling and taxiing. When you put a higher load on the system and there’s more fuel flow,

Are the fuel pumps variable speed then?  And ramp up in speed to increase flow as engine demand increases?  The fuel is filtered before being injected in the engines?  And if the contaminant is making it to the engine injection, wouldn’t that throw off your air to fuel ratio even at start up checks and taxing?

[WallFlowerActive]

I do know some ford diesel trucks have issues with the fuel pumps coming apart and ruining the fuel injection system?  Contamination could be cover for foreign parts intrusion from failed mechanical parts?

[WallFlowerActive]

 Contamination 

I would think military aircraft in wartime would be at more risk for fuel contamination?  Do military aircraft have more robust systems to deal with aircraft fuel contamination than civilian passenger jets?  I would design, say a cargo jet for the military as if the fuel system would have water contamination at some point?

[Zaphod58]

Are the fuel pumps variable speed then?  And ramp up in speed to increase flow as engine demand increases?  The fuel is filtered before being injected in the engines?  And if the contaminant is making it to the engine injection, wouldn’t that throw off your air to fuel ratio even at start up checks and taxing?

It isn’t making it to the injection. Usually what happens is when the fuel flow increases, the pressure breaks something loose, it moves into the fuel lines and gets stuck, restricting the fuel flow, reducing the pressure to the engine, resulting in reduced power. Depending on where in the take off it happens, it may be too late to do anything about it. 

They have multiple pumps in the fuel system that run at different pressures. The wing tanks run a lower pressure than the center body pumps, and the boost pumps run lower than the wing tanks. I believe the 787 uses both variable speed and variable frequency pumps which allow them to be supplied power from different systems in the event of a failure, but I’m not a fuel systems expert.