Discuss the problems and solutions to all of the situations that Pilot X finds himself in.
User avatar
By G-BLEW
#975120
Hung on the rack

Why does Pilot X break all the rules? A fine summer day and an aircraft you know like the back of your hand is no excuse, in this tale by Nick Lambert


Pilot X, standing in his back garden, was dividing his attention between flipping burgers and watching aircraft passing overhead. Not a cloud in the sky and none of the haze often associated with hot summer days. His father, following his son’s gaze, suggested an impromptu flypast for the family gathering. Before the old man had a chance to change his mind, Pilot X handed his father the tongs, and disappeared. The strip was less than five minutes down the road. He could pop into the petrol station for a can of fuel and still be buzzing the house in 20 minutes.

As soon as he swung into the car park, he could see the aircraft had already been pulled out of the hangar, probably to allow another out, although the old man may have already taken her for a spin and not mentioned it. The place was deserted; it looked like everyone had gone flying today.

G-XXXX was a Rotax-powered two-seater, which his father had built while Pilot X was at university. Pilot X had helped with the build in the holidays and knew the aircraft inside out.

He did a quick walkround, but since only he and his father flew the aircraft, he didn’t expect any surprises. Similarly, everything inside seemed in order, so he was soon calling, "Clear prop!" She started instantly. He fiddled with the switches while he waited for the temperatures to rise. Everything was fine, except the fuel pressure didn’t seem to rise when he flicked the electric pump on. This didn’t worry him unduly; he knew some Rotax installations didn’t even have an auxiliary fuel pump. Nonetheless, he made a mental note to ask his father about it.

Checks complete, he lined up on the long, westerly runway. A last glance at the windsock confirmed a stiffening southerly breeze. Holding appropriate aileron he applied full power. Despite being only one-up, acceleration was a little sluggish, which Pilot X put down to the high ambient temperature. What was more worrying was that the engine ‘coughed’ just as he was about to rotate. He paused for a second, but as normal service had been resumed, pulled back on the stick.

At 800ft, Pilot X retracted the flaps. He was just about to turn right, crosswind, when the engine stopped. Instinctively he lowered the nose to maintain airspeed. At the same time, he unsuccessfully cranked the engine. 'Pull yourself together,' he told himself. This was far too low to be messing around trying a restart; he needed to assess the options while he still had some. Ahead was a vast field that had hosted a hundred practice engine failures on take-off.... the difference now was that the field had been roughly ploughed and the ground was rock hard. It didn’t take much imagination to see the aircraft would be shorn of its landing gear and on its back within a few yards. There was a copse to the left... and the fields to the right still hadn’t been harvested.

Squandering options

The only chance of saving the little aircraft, which had had so much love and attention invested in it, was to land back on the strip. He knew a gentle turn would take him further from the end of the runway, so he banked hard. He thought he felt some buffeting and, terrified, released the back pressure. Landing on the plough might not kill him, but stalling-in definitely would. He seemed to be dropping like a stone and had not even completed half the required turn.

'What are you doing?' he screamed at himself. He knew that you never turn back, but here he was, squandering altitude and options, while trying to salvage an aircraft that was comprehensively insured. Having completed the course reversal, he found he needed to keep the turn going quite a bit before he was pointing at the strip. He was now down to 300ft and for a moment it looked like he might make it. Then slowly, inexorably, his reference point started slipping up the windscreen. He was already clean and at best glide speed, so there was nothing left to do. In desperation, he turned the engine over, but it was no use. At 200ft it was clear he would be landing in the plough, and hitting the airfield’s boundary hedge with quite some force, if by some miracle the gear didn’t collapse.

Noticing the windsock, he realised that by turning another 30° he could, at least, land into wind. Losing a bit more height now wouldn’t change a thing, so he made the turn. From 50ft the surface looked terrible. He knew his best chance was to land as slowly as possible. Belatedly he remembered the flaps. Suddenly applying flap caused the aircraft to balloon alarmingly. He applied full throttle, but predictably there was no response; his airspeed was terribly low but he didn’t dare move the stick forward so close to the ground...

As Pilot X regained consciousness, he heard a blackbird singing. The only other sound was the ticking of the cooling engine. The aircraft had indeed flipped over and he was hanging in his harness. Something was dripping onto him; his first thought was fuel, but it turned out to be blood, shorts and flip-flops not providing much protection against mangled rudder pedals and a shattered panel. As he became more aware, he noticed he was losing a lot of blood from a deep gash in his thigh. He started panicking, afraid he would bleed out. He tried to scream but produced only a whimper...

After what seemed like hours, but was actually less than 20 minutes, he heard the noise of rotors above. He wept as he recognised the lurid paint job of the air ambulance; he knew it had been a close shave.


QUESTIONS

1 What caused the engine failure?
2 What could Pilot X have done better?
#975128
Well that sounds to me like it has to be carb ice during the warm up and taxii building up against the wall of the carb body and allowing fuel to continue to pass through the middle (imagine the hole in a polo mint). Especially as there is no real temperature compensation from a warm engine as the engine block and surrounds were still warming up during the warm up and taxii.

On application of full power when starting the take off run, the engine would have sounded quite normal but because of the restricted flow (which would affect pressure) would have failed to achieve full static revs. This symptom would then not be apparent as the aircraft started to roll and the revs increased as the prop/engine now has less strain on it.

As the aircraft eventually reached take off speed and commenced its climb out the engine would now under full power have been nicely warming up and the increased heat would have transferred to the carb body causing the release of some of the ice from the carb wall. The cough was probably a very small amount of ice/water passing through the engine or an over rich restricted engine complaining.

Eventually though, the now hotter engine under full power would have warmed the carb body even more. this would cause the ice to melt from the "carb wall side" of the ice and not from the inside of the carb (as it does with carb heat). As that happens the unmelted Ice loses it grip on the carb wall (think polo mint breaking up) and may have collapsed inwards blocking the fuel air mix and causing the engine to stop.

No amount of cranking will restart the engine, its unlikely too that application of carb heat at this point will provide sufficient heat to cure the problem. If it did melt the ice then a huge blob of water might prevent re-ignition.

What could the pilot have done:

1. It should be a compulsory part of training that Pilots should always at the start of a BBQ, have a few beers themselves. That way they have a perfect excuse not to drive or fly!

2. Application of carb heat: Quite long periods of the application of carb heat on the ground are important. Applying carb heat just because your POH or FI say's you must check its working is not sufficient (in my opinion). Of course by all means you must ensure its working but you should also leave the heat in for an extended period and pay proper attention to the rev counter before during and after carb heat application to check for ice. Did the revs as the carb heat is pushed off stay the same as they were before you applied it? Or did they increase slightly? It is your best warning of ice being present. Also try using your your ears, Rotax and Continental engines I notice can sound a bit different under carb ice.

3. Checking the engine has achieved full static revs on the application of full power just before the aircraft rolls at the start of the take off run is essential and the last warning you'll get. Do you know what the static revs at full power should be for your aircraft?

4. The hardest thing is not turning back if height below 1000ft. Look for a safe as possible place to land somewhere ahead. Aircraft can always be rebuilt, pilot safety is more important. The next hardest thing is to fly the aircraft first, but who am I to criticise, I have never had a complete engine failure.

I had this carb ice scenario happen to me in a Robin HR200 and got away with four extremely loud and sharp bangs as the ice/water passed through the engine as it amazingly continued to run. It frightened the living death out of me at the time. Later on the ground at Bourn whilst looking around the engine for something wrong, Lindsay Brown came up and kindly explained what had really happened and what to do. From then on I ensured that I used carb heat properly and also monitored static revs to never let it happen again.

Perhaps its paranoid but having completed all checks at the hold, I also tend to actively manage carb heat whilst awaiting other aircraft to land or I just apply carb heat for the taxii and line up, rather than risk it. :x
User avatar
By Keef
#975227
I like Jim's answer, but I wonder why the fuel pressure didn't increase when he turned on the electric pump.
Usually, you can hear an electric pump running: he should as part of his pre-starting checks have turned it on before starting, when it would have been audible. He would therefore know it was working (or not). May there have been something restricting fuel flow?

Turning back - only if you have enough height to do so. We all know the minimum turn-back height for our regular mounts, don't we! Minimum speed landing in line with the furrows (never across) is preferable to spinning into them.
By mur007
#975251
Could it have been that he ran out of fuel and that caused the engine to stop? I'm thinking of the low fuel pressure - assuming the electric pump was working, would it have read low if he was low on fuel? The aircraft had been pulled out and the place was empty so it was possible that his dad had indeed flown it earlier and not re-fuelled and/or someone had been stealing fuel. I know it says that he planned to stop at a petrol station but maybe in his excitement he forgot? His pre-flight checks do not sound too thorough so it is something he might have missed as a result.

Alternatively - as Keef suggests - maybe some kind of blockage blocking the fuel supply, or possibly contaminated fuel (did he strain the fuel?)

I know that getting carb icing is entirely possible on dry days (the sky was cloudless) but would he have built up enough ice to cause a sudden and total engine failure so quickly?
User avatar
By Jim Jones
#975433
My thoughts were that he had failed to visually check the fuel level before flight. Lots can happen to an unattended aircraft, including previous check for water leaving the drain cock partly open as well as theft or previous user not refilling or yet logging the flight.

Oil and fuel visual check before every flight, even if you have been the immediate previous user.
User avatar
By Gertie
#975548
I think this one is a trick question.

It's an attempted murder. The father sabotaged the aircraft (sounds like something in the fuel system) then suggested the son take it for a flight.

In real life of course this scenario is completely unrealistic as there's no way the guy wouldn't have been drinking whilst tending the barbeque, and he would therefore have refused the suggestion.
User avatar
By Capt Edmund
#975711
Legging it off to carry out a rushed prep for flight is just like taking a hot poker to the slices of gruyere that make up the risk-management of flying. As for what went wrong, I'd have a punt at a lack of fuel being pumped to the engine. Assuming that the electric pump has failed, evidenced by the lack of pressure change, there may be insufficient pull from the engine driven pump to feed the engine either due to the installation or a failure of the pump. The lack of full power, cough at rotate and the conk-out when deselecting flap would suggest that the feed was on the limit of what could be provided by gravity and was critically affected at differing pitch angles.

As for what could have been done better it's all in the pre-flight and reactions to thing outside the ordinary. He was obviously in a hurry (I won't even go into whether he got NOTAMS, Wx and the like!) and missed out on the opportunity to listen to his father before he went or investigate why the ac may have been out. After that he should have conducted a proper walkround and, later on, stopped to investigate why he couldn't get a Px change with the pump or why he was struggling to accelerate.

Of course, not bothering to refuel the ac would have had a similar effect as it coughed and spluttered sucking in the dregs and it may have un-primed the pump which would have caused the lack of Px change.

Oh yeah, and land within 30 degrees ahead!
By Lambada Crazy
#981011
Classic Example guys of the fuel in the "Off" position!

Ive seen this happen before;


He did a quick walkround, but since only he and his father flew the aircraft, he didn’t expect any surprises. Similarly, everything inside seemed in order.


Everything was fine, except the fuel pressure didn’t seem to rise when he flicked the electric pump on


The gravity and electric fuel pump are two different items. The gravity pump will always operate (unless broken), and you have a back-up, electric pump for critical phases of flight in case the mechanical one fails!

This didn’t worry him unduly
Uh oh!!

What was more worrying was that the engine ‘coughed’ just as he was about to rotate. He paused for a second, but as normal service had been resumed, pulled back on the stick.


Probably due to the lack of fuel coming up the lines to the engine, that when the nose started to rise, the air went to the carb first and gave a quick cough!, when he paused, the fuel in the line ran back to the carb and gave him his engine back.

This was far too low to be messing around trying a restart
I know people can panic in a bad situation, missing critical things like the fuel in the off position!



Depending on aircraft type, the fuel line can be as long to run the engine for 6-8 minutes. Your average PA28s engine will run for about a minute before cutting out. But ive seen a piper cub run for several minutes. Once you start increasing power, the fuel demand picks up.

Just my opinion....
By mixsfour
#985392
Late response due holidays (and I've read the published explanation). Andy has a point here as the original scenario tells us Pilot X fiddled with switches during the warnup. Of course he should have checked the fuel cock during his power checks.

Lack of fuel pressure when the pump was switched on would have me worried especially on Mogas, any engine hesitation on the runway would have me close the throttle and apply the brakes. He had two warnings there and ignored both!