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Fuel Leak?

之前有人問SUSPECTED FUEL LEAK 有咩要做?

第一件事我地要會知Fuel leak? But How?

正常我地每次飛, 每30分鐘都要做fuel check, 要monitor fuel consumption; 咁先可以盡早發現fuel leak.

Airbus 有ECAM; 通常fuel imbalance 會係一個ECAM . 因為好小Leak from both tanks, 所以如果有Fuel imbalance, 唔好心急 ECAM action,開 crossfeed. Identify 無fuel leak 先好開!

除左Imbalance之外,仲有咩方法/hints知道fuel leak?

A fuel leak may be detected by:

‐ The sum of FOB and FU is significantly less than FOB at engine start, or is decreasing, or

‐ A passenger observes a fuel spray from an engine/pylon, or a wing tip, or

‐ The total fuel quantity is decreasing at an abnormal rate, or

‐ A fuel imbalance is developing, or

‐ Fuel quantity of a tank is decreasing too fast (leak from engine/pylon, or hole in a tank), or

‐ A tank is overflowing (due to pipe rupture in a tank), or

‐ The Fuel Flow is excessive (leak from engine), or

‐ Fuel is smelt in the cabin.

If visibility permits, leak source may be identified by a visual check from the cabin.

WHEN A LEAK IS CONFIRMED LAND ASAP

即刻搵地方Divert, 因為未搵到leak source同isolate source 之前, 你唔知部機仲可以飛幾耐~

之後就要搵leak source 同isolate 個source (from the Tank?the pipeline? within the engine?)

搵到leak source, 停左個leak 先可以知到部機重有幾多usable fuel 同重可以飛幾耐~

如圖, 有d case 我地要shutdown 個engine 先可以identify 到 leak source( engine or tank)

真係要冷靜處理~開錯crossfeed 就 fuel starvation!

下個ACI 講Air Transat Flight 236 好唔好?

留下言la~

7 comments

7 Comments

ATVpilot

Apr 24, 2020

let me know what you think about this~

Dream to fly

Apr 21, 2020

Thank you for the explanation! Indeed support and Looking forward to Air Transat Flight 236 ACI post! Interesting accident where the trim tank design of Airbus misleads the pilots from recognising the fuel leak.

First follow-up question is about the single-engine operation, when one of the engines is suffered from fuel starvation due to the wing tank leak on one side, would it affect the manoeuvrability of the aircraft and hence need to increase the VMCa/VMCg or even need a higher Vref on landing? (because you may need extra aileron deflection to counteract the weight imbalance + asymmetric thrust at the same time, terrible!!!) Secondly, I am a bit confused with the leak source identify flow (of a fuel leak), maybe I write it out first: Engine/Pylon --> Wing Tank --> Centre Tank / Trim Tank / APU Feed Line, please correct me if I am wrong.

A term Fuel Loss Reduction has been mentioned in the QRH for a few times, what can actually pilots do inflight to reduce fuel loss apart from isolating the leak source?

Furthermore, the QRH shows that DO NOT use reversers for LDG, I understand that using the fuel leak side's reverser may spread the fuel leak further or in the worst case cause a fire. But why can't we use the remaining reverser? As it is still useful for landing deceleration.

Finally, in cruise, besides fuel checking, is there any other figure (maybe FL or weather-related ?) do pilots need to check for? Those checking procedures would usually be completed by PF or PM?

ATVpilot

Apr 23, 2020

Replying to

@Dream to fly

Thanks for your good question~

Of course, weight distribution is a factor to determine VMC; but as long as the imbalance is within tolerance, it shall provide acceptable manoeuvablitilty. But of course, as good airmenship, we need to be aware about the imbalance and the handling.

Besides that, quick question! would you rather have an empty tank, or tank of dead weight (fuel) on the dead engine side?

For your second question, I will make a flow chart to help your understanding.

Fuel loss reduction means, when the leak is identified from the one tank; we follow procedure to transfer fuel from the leaking tank to other tanks; so we can reduce the fuel loss.

You are correct with the reversers. The biggest concern is Fire. Therefore, if performance allowed, we won’t deploy the reverser when fuel leak.

Flying is very dynamic; we need to monitor all system parameters(inside) and also monitor outside threats (like Wx/Traffic…etc); then, based on the situation, react to the situation.

Dream to fly

Apr 26, 2020

Replying to

@ATVpilot Besides that, quick question! would you rather have an empty tank, or tank of deadweight (fuel) on the dead engine side?

Hum.....tough one, I would say it depends. If I am fly a twin-engine aircraft on ETOPS/EDTO route, losing one engine makes me fall into a quite critical condition. In that condition, I would prefer to have some more fuel for my diversion. Assume that I can use the crossfeed to supply fuel for the "live" engine. (But you mentioned dead weight in the question so I think maybe the fuel on the dead side is unusable anyway? )

So, if I am close enough to the alternates (or fuel in both sides' wing tank is non-transferable), I would really prefer an empty tank because it could reduce your LDG weight, which could increase your aircraft manoeuvrability as the sizes of your control surfaces are always unchanged. Otherwise, in some case, I may need to find a place to dump my fuel and reduce my LDG weight.

Hence, a smaller LDG weight also brings you a shorter LDG dist (more available LDG sites/alternates), smaller tire pressure and less chance of catching fire in a force LDG.

ATVpilot

Apr 27, 2020

Replying to

@Dream to fly

Thanks for your reply!

Of course, if fuel quantity is a concern, I would want to have more usable fuel. However, as we discussing about critical engine and Vmca, our first priority is control the aircraft and return to land. So the real question would be , is the aircraft fly better with an empty tank or fuel in tank (weight )? Which one is better considering control-ability?

I tried to look for some reference, but I haven't found it yet. with my understand, I think the aircraft is more controllable with an empty tank on the dead engine side (More Fuel and Weight on the live engine side).

I will look for an explanation. Let you know when I find it~ Meanwhile, if anyone got any idea~ please help as well~

ATVpilot

Apr 21, 2020

@Gary Law

During flight planning, waypoints are usually plot within 30mins; and it will provide not only time/distance, but also fuel computation information.

It will include estimate figures of Fuel used, fuel consumption and fuel remaining. Every 30 mins, when we overfly the waypoint, we will observe and jot the actual figures from the engine display. Compare the figure if there is any abnormality. Also, we can also use (FOB+FU)-Block=Discrepancy.

Although I don’t have much experience with Boeing, but I believe all aircrafts has similar concept in terms of detecting fuel discrepancy. FOB+FU shall equal to Block fuel.

In general, fuel check per 30mins is a good practice to early detect fuel leak. (A350 has a fuel leak detection system.)

Of course, if the engine is old, the performance shall deteriorate; however, that discrepancy is relatively small (maybe 1~2% )

Gary Law

Apr 20, 2020

Thank you so much for the detailed explanation. How do you conduct the fuel check every 30 mins?

Is there a different form for Boeing, AIrbus and ATR?

Also would it also be an early detection of fuel leak if one of the engine has an abnormal fuel flow? (But I guess some of the engines are perhaps older and require more fuel to run?)