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Shaky calculations: safety vs commerce

by Nancy Jackson Media and Communications Officer

How much fuel should a pilot take to ensure their flight is a safe one? It’s a calculation pilots have to consider every time they take to the air. Lots of factors need to be considered when making that judgement, including the predicted weather and operational factors. But what about commercial factors? In this article a BALPA member examines the issue and describes a time when he had a close call with fuel levels.

A retired pilot writes:

I was very interested in Captain Andy Brown’s experience, when a runway closure at Gatwick exposed the fact that many aeroplanes were flying with more air in their tanks than fuel (The Log, winter 2018).

One Sunday morning I, too, experienced that ‘sinking feeling’ he mentioned, when time and fuel no longer seemed in sync. That day we were only CAT 1 capable but, while the destination weather was expected to deteriorate, the forecast had it comfortably above our minima until well beyond our ETA.

“…our fuel was close to the minimum required.”

Nevertheless, I had decided to uplift a little extra fuel – just in case – until it became clear that I would incur an unjustifiable delay, given that technically I already had enough fuel for the flight.

Sadly, the forecast was wrong. As we approached our destination, their visibility dropped below CAT 1 minima. We entered the hold while my First Officer called our alternate to check that their weather was holding up, and that an expeditious approach would be available if we appeared in their sky. They confidently reassured us on both counts. It soon became obvious that the RVR down below was still dropping, so we cut our losses and diverted. By now our fuel was close to the minimum required.

“…we did not have enough fuel to safely go anywhere else…”

As he put us onto a downwind heading, our alternate’s approach controller told us there was to be no delay. However, as we passed abeam the airfield, he suddenly sent us towards the NDB to join the hold, “delay not determined”. What? A glance at the fuel gauges confirmed that if it became necessary to make a second diversion, followed by an instrument approach, I would be relying on some shaky calculations and luck, a combination a pilot should never trust. Put simply, we did not have enough fuel to safely go anywhere else – that is what minimum diversion fuel often means.

I bleated that we were getting low on fuel and asked the controller why we were being put on the naughty step. “Runway closed,” he replied. An aircraft was stuck on the runway with burst tyres. I checked my options, including if things got really desperate an ILS-to-visual followed by a landing on the parallel taxiway. However, it turned out that the flat-footed aircraft was not an Airbus or a 737 but a light twin, and strong men were assembling to manhandle it off the runway. The controller predicted the runway would be clear in 10 minutes.

The hold was cancelled and instead we were given round-the-houses vectors to a very long final, with the magic words, “cleared to land” coming late in the proceedings. Nevertheless, we arrived safely, albeit with a few extra grey hairs.

Safety vs commercial considerations

So, what to make of this sorry tale? Well, let’s go back to basics – when you fly, what comes first: the safety of your aircraft or ‘commercial considerations’? And what about those three most useless things we learned about in basic training – sky above, runway behind, fuel in the tanker? Are we really so advanced that they no longer apply? Or are we ignoring them in order to satisfy commercial considerations?

Here’s a thought: aircraft safety involves redundancy – two pilots, at least two engines, several sources of electrical power, and back-up undercarriage extension. Operationally, we build in redundancy by having an alternative airport and, if our destination is using LVPs, two alternates. The loss of an engine, particularly in a twin-engine aircraft, is treated as an emergency regardless of the aircraft’s performance. Why? Because the redundancy has been used up, if the other engine fails the aircraft goes down. So what happens when you start a diversion with only enough fuel to reach one alternate airfield? Well, once again you have exhausted your redundancy, so if the alternative fails, you have a problem.

In the UK, we tend to think of an airport failure in terms of weather. However, weather aside, here is an incomplete list of things that have either prevented me from landing, or caused me exceptionally long airborne delays: disabled aircraft blocking the runway, large animals loose on the airfield, runway damaged, lighting failure at night, terrorist attack, no parking available, no fire service available, grass fire next to the runway, large number of simultaneous inbound diversions, runway flooded. Putting weather back into the frame, I have also seen some seriously inaccurate forecasts, including one that farcically predicted a 60 knot headwind that materialised as a 60 knot tailwind. We were happier than the people coming the other way.

If your alternate has several runways, there is sufficient redundancy to cope with most of the events listed above, but if it only has only one runway you either have to rely on any problem being solved before the fuel runs out, or cobble together a plan that may require as much luck as judgement. I have heard some hair-raising tales.

Commercial thinking says it is worth sending aircraft out with just the legal minimum fuel because the savings overall – less fuel means less consumption – are greater than the losses incurred by having the occasional – avoidable by carrying more fuel – diversion. However, because of the lack of any further redundancy, I would argue that there is a safety issue if the diversion airfield has just one usable runway, or when – regardless of what the forecast says about timing – the weather is deteriorating.

Remember who is responsible! 

A final thought: unless the rules have changed, the person who bears total responsibility for deciding on the amount of fuel needed for a flight, based on his experience, judgement and gut feeling, is the captain, supported by the first officer – not the company accountant, the operations manager or even the CEO.

I am retired now, so argue it out among yourselves. However, I will say this: in my final years of flying the line, I increasingly heard aircraft whingeing about being low on fuel, sometimes with a PAN, even as they approached their destinations. I don’t think that’s right – do you?