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Pawnee Fuel Starvation - The Graphs Don’t Lie

May 3, 2017

 

 

 

SYNOPSIS

On 4 January 2003, at approximately 1100Z, after refuelling the aircraft to maximum capacity at FASH (Stellenbosch), the pilot departed to the Green Point area, towing a banner.

While flying over the Camps Bay area at 300 ft AGL, in fine weather conditions, the aircraft went inverted due to turbulence. The pilot managed to right the aircraft, and decided to return to FASH. The engine then started running rough, steadily lost power and failed. A forced landing was executed on an open field, adjacent to the Hamilton Sports Field in Green Point Commune, near Cape Town CBD.

The pilot decided not to release the banner due to potential injuries to pupils on the ground. The pilot sustained serious injuries and the aircraft was extensively damaged. The pilot held a valid licence and a valid medical certificate, but was not rated for banner towing.

The aircraft was type accepted in South Africa and, according to available documentation, was properly maintained.

The engine was dismantled and inspected, but apart from accident related damage, nothing was noticed that could have caused the engine to lose power or to fail.

The aircraft was operated under Part 135 of the Civil Aviation Regulation of 1997, under the licence of Cape West Aviation (Class III Air Services Licence No. G495D). This facility was audited by the CAA on 13 November 2001.

The AMO file at the CAA couldn’t be located to confirm the CAA audit status.

 

PROBABLE CAUSE

Although fine weather conditions prevailed at the time of the accident, the wind was very strong and gusty. This will cause a considerable increase in the fuel consumption and can, therefore, be considered as a highly probable cause to this accident. In addition, the significant increase in drag from towing the banner would have further increased fuel consumption.

The pilot did not have a rating for banner towing. His inexperience in this regard could have contributed to miscalculations with fuel consumption as well as manoeuvrability of the aircraft.

The pilot was flying the aircraft at 300 ft AGL to ensure proper visibility of the banner to people on the ground, leaving virtually no options when the engine failed.

 

JIM’S ANALYSIS

There seem to be a couple of things going on here, but the main one was a total lack of respect for the fairly simple concept of fuel planning.

What goes on in people’s minds? When did you last run out of fuel in your car? So why do pilots, at all levels, think it is OK to push their luck with fuel, obviously endangering lives – particularly their own? Sorry, I just don’t understand it.

If I am flying a Cherokee and both gauges are below a quarter, I feel really uncomfortable, although there is probably still a good hour’s worth of flying. But then you shouldn’t work on probabilities – you keep a fuel log. From the log, you know, with reasonable accuracy, how long you can safely stay in the air. In fact, I am always amazed by how accurate POH fuel consumption figures are.

When your calculations say a tank is about to run dry, that’s exactly what will happen.

This aeroplane was working hard. It was at the coast and using a lot of power. We don’t know how big the banner was, but banner towing needs quite a bit of extra poke to overcome the drag. And the problem is magnified by turbulence. The more severely you are being chucked around, the more power you need to keep the aircraft under control.

If the turbulence is so severe that it turns the aeroplane upside down, which I don’t really believe – I will tell you why in a minute – then you would want full power, and you would be drinking gas.

The guy had nearly a thousand hours – a stage where many pilots begin to think they are bullet-proof – but, he had less than a dozen on type. Surely that is more reason to trust the POH, and the big red ‘Low Fuel’ light, which would have been burning for almost half an hour.

I suspect the fact that he didn’t bother to get rated for banner towing is an indication of a rather cavalier attitude, which might account for the way this flight was conducted.

Strangely, logbook hours don’t seem to mean a lot when it comes to taking a chance on fuel. In last month’s Accident Report on a Dakota, we saw a pilot with 24,000 hours gamble on fuel, in perfect weather. He lost the gamble and crashed.

Actually, I would say that low-hour pilots often have more respect for fuel planning than the guys with bulging logbooks.

Back to this particular prang. Take a look at the Lycoming graph for that engine. I can’t see how he could possibly have used less than 16 US gallons per hour. Full fuel in a Piper Pawnee is 36 USG. He took off at around 1100Z and crashed a little over two hours later. The fact that he ran the tanks dry exactly when he did indicates that the graph was extremely accurate. A guy with a thousand hours should know this.

I suspect my bleating about fuel-related accidents is like suggesting to taxi drivers that overtaking on white lines could be hazardous to one’s health. It just doesn’t sink in. Each one of us seems to think we are immune to running the tanks dry. There just has to be enough gas to get us home.

Jim’s warnings are for other people – not me.

When this guy ran out of fuel, at 300 feet AGL, he was 30 nm from home. Also, assuming the aircraft was serviceable, that low-fuel warning light must have got his attention. You have to wonder when he was planning to return to base.

What was going on in his head? Doth the mind not boggle?

Actually, I do have an idea what was going on in his head. When a company contracts you to tow a banner, they only pay for the time you are pulling the banner over their target area. You can see where this is going. The pilot’s watch was showing income in Rands and cents – not fuel remaining in the tank.

Now, back to why I don’t believe he was inverted at any time. He had been flying in that area for at least an hour and a half. He would have noticed when the wind started changing direction, or becoming too strong. I can’t see it happening suddenly with no warning. No one in their right mind would be flying at that height in that sort of turbulence.

Also, I suspect he was looking for a reason to explain away the engine failure. Going upside down caused the engine to run rough and then fail. Really?

 

WHAT CAN WE LEARN?

The same old things that I keep bleating about:

Thou shalt feed thine aerial steed.

Thou shalt not put money or People Pleasing Pressures (PPP) before safety.

Thou shalt harken to that little voice that says thy fuel reserves are low.

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