Here’s a presentation pulled together by a guy that crashed his RV-9A. Spoiler: fuel mismanagement and then a stall over the airport – severe injuries.
Some good reminders in this deck.
https://docs.google.com/presentation/d/1hBMikFdqinAP9IPx25YXEJbTahC_AxD8b9fyFrgK2iQ
BTW: did you know that Montana has about 1.1 million people, and is about the size of Germany?
eurogaguest1980 wrote:
Some good reminders in this deck.
Reassuring to see that I already do the things he recommends…
But I was a bit surprised by this bit: “I did not know that air ingestion could cause engine pump failure”
Neither did I. Does he mean actual failure of the pump or that the pump is not able to recover from a situation where it is filled with air rather than with petrol?
Airborne_Again wrote:
Neither did I. Does he mean actual failure of the pump or that the pump is not able to recover from a situation where it is filled with air rather than with petrol?
Yes, indeed, few fuel pumps are self-priming and the procedure is typically in the POH. The fuel pumps I encountered where all non-self-priming so far, so I am aware of the booster pump necessity in case of engine problems, but I wonder whether this also has to do with ‘Experimental’?
Not all pumps are self-priming, and those that are have their limits. Also, a very small air leak on the suction side of a pump will greatly reduce its ability to self-prime.
Every low-wing aircraft I have flown has as a standard procedure to have the aux fuel pump on when near the ground, takeoff, landing, and any kind of “aerobatic” flight. The fact that this pilot didn’t know this was also very surprising.
The “experimental” part comes into play as he said that he didn’t have a POH/AFM. Well, it was his job to write this, and of course that means it was his job to fully understand all his systems.
Probably lessons for other homebuilders more than for those flying certified aircraft, but I thought this was interesting.
Another topic to discuss is the stall while over an airport, which is the real reason this fuel mismanagement event turned into a crash.
Immediately the engine falters – electric pump on, carb heat, change tanks. Fast.
If the engine picks up when electric pump on, (due to fuel in pump) it’s probably fuel. Changing tanks should sort.
Carb ice sounds different to fuel starvation.
I’ve had:
Pa28 – accidentally ran tank dry.
Pa38 – accidentally ran tank dry
Jodel DR1050 – air leak at pump, vapour lock in gascolator, blocked finger filter in rear tank, accidentally ran rear tank dry, fuel leak at connection to carb.
All the “tanks run dry” events involved wrong fuel indications..
The vapour lock events were at take-off with room to stop. Not solvable without a shutdown.
The other Jodel events allowed me to return. Problem detected when I changed to rear tank and switched off electric pump in the climb.
High wing aircraft have gravity feed. Someone modified an RV to have 3 fuel positions like Cessnas. “Both” ran a tank dry, leading to a ditching, as the pump chose the easy option of pumping air.
Maoraigh wrote:
Pa28 – accidentally ran tank dry.
I inadvertently ran a tank dry in my Cessna 140 (or more accurately, below the level allowed for takeoff, below about 1/4 of a tank there’s a risk of unporting on climb out).
I was doing a touch and go, and had likely just mechanically switched tanks on downwind without verifying the quantity in the tank I was switching to. On the go, at about 50 feet, the engine started spluttering (and with FAA 50-foot standard trees ahead, too). I think my hand reached a significant fraction of the speed of light going to the fuel selector…
alioth wrote:
I inadvertently ran a tank dry in my Cessna 140 (or more accurately, below the level allowed for takeoff, below about 1/4 of a tank there’s a risk of unporting on climb out).
Just to add one more aspect, look at the fuel selector and test it frequently. I had almost an incident once after minor maintenance. Runup was ok, start roll was slower than usual and I immediately turned around and landed back on the airport doing one traffic pattern. Upon inspection we found the fuel selector on OFF … hadn’t checked it on the rush fool me. I bought a new fuel selector, because the old turned out to be u/s. Now I am back to my extended checklist, frequently checking the fuel selector really cuts off the engine.
MichaLSA wrote:
Now I am back to my extended checklist, frequently checking the fuel selector really cuts off the engine.
I think it’s good to test the fuel selectors from time to time, but I would recommend not doing this just before a takeoff.
If you are in a low-wing aircraft, you test the left-right ports almost every flight, at altitude – no worries. If you want to test the off function – which I honestly don’t recommend outside of perhaps during a 100 hour or annual inspection – do it after you land, and ensure that the engine quits. This will reduce (but not eliminate) the chance that the next person won’t try to take off with the fuel selector in the wrong position.
I simply don’t touch the fuel selector between startup and and takeoff – if I’m on the left, I leave it on the left, even if I have a bit more fuel in the right tank. If my left tank is so low that I feel the need to use the right tank, I’ll just add fuel.
Fuel selector changes at the wrong time have killed many pilots.
I did not have muscle memory for engine failure- just academic recital
The back side of relying on check lists perhaps. Learning check lists by heart and developing muscle memory is the only thing that works IMO, at least when time is of the essense. Very open and honest explanation of what happened in the accident.
Lots of focus on the fuel pump and boost pump, the operational principles, placing of switches and usage. A red herring with regard to the accident IMO. What is truly lacking is planning of the flight which seems to be completely absent.
Maoraigh wrote:
High wing aircraft have gravity feed. Someone modified an RV to have 3 fuel positions like Cessnas. “Both” ran a tank dry, leading to a ditching, as the pump chose the easy option of pumping air.
Aircraft fuel system designs are non-trivial. The “Both” position is not typically used on low-wing aircraft for the quoted reasons. This problem is minimised on high-wing aircraft since there is at least 1m “head” pressure from even an empty tank (the line from the tank to the valve), to avoid sucking air into the lines. .
Air and fuel vapour in the system, contaminant draining as well as pump priming are some of the major considerations.
Heavy fluids tend to go to the bottom when under gravity and light ones go up…so there should always be a pump in the lowest part of the system, to ensure it can be primed easily. The system is usually designed so that there are no low-points, other than where the boost pump and gascolator and associated drains are located. All lines should be downhill from the tank to the pump, and uphill from the pump to the carburettor/injector (ie no “valleys” or “peaks” in the lines, only valley should be at the boost pump, peak at the carburettor/injector and fuel tank) . That way the possibility of vapour lock is minimised as all gases are quickly pumped out of the system into the carburettor/injector.
Carburetted aircraft have their own “header” tank in the carburettor and can even do away with a boost pump, especially if high-wing, but fuel injected aircraft , aerobatic or not, frequently use a separate “header tank” or “collector tank” which should always be full when in normal operation. The fuel boost pump is either inside such header tank or at the same or lower height. This ensures that temporary unporting of fuel feed from the main tanks does not stop the supply of fuel to the boost pump or the engine.
Of course high-wing aircraft have an easier job, but low-wings have a hard time ensuring the tanks are higher than the critical low parts of the system.
With “flat” wing tanks, if dihedral is high (Arrow, Bonanza, Mooney, Commander…) , even on injected aircraft you can do away with header tank, but with low dihedral (Cessna 172, 177, 210) it is almost a requirement, as temporary unporting of fuel lines at the tank is a more likely possibility.
So you will find older, carburetted 172’s have no header tank or reservoir
but the injected 172S’s do.
The Cessna 210 was a good example of the issues that can come up with the fuel system when changing the flight regime.
Even with all the experience, Cessna 210’s had several iterations of fuel systems. For the stated reasons, a better engineering design was the initial three position L, R, OFF selector vs the better human factors design of the BOTH position. The latter is very difficult for a low-wing, as @Maoraigh’s Rv example, but on the high-wing 210 it was possible and hence introduced from 1982 and on.
210’s had always been injected since 1960 hence there had always been header tanks. Two of them on the older L-R-OFF systems, one only on the L-R-BOTH systems.
Cessna however found an unexpected problem: the fuel injector system on Continentals have a gas separator at the pump, and air/vapor is thus returned to the tank via a separate line from the pump, as all Centurion, Bonanza, Seneca, and Conti Mooney owners know. Lycomings pump gas/vapour through the fuel injectors themselves.
In the late 60’s turbocharging was “sold” as a great idea on Conti-powered Cessna 210’s with ceilings as high as 30000ft. However, the great climb rate into the high teens and low twenties with warm fuel resulted in high amounts of fuel vapor being generated (low atmospheric pressure) on any low-press+high-temp parts of the fuel system before the fuel had had time to cool down at altitude, resulting in fuel flow fluctuations and even engine failures caused by vapour lock in the lines. This was compounded as the amount of vapour returned to the header tank was higher than it could in turn return to the main tank, thus ending up with vapour-filled headers… This was worse on the P210’s since pilots were flying them at high-altitude more often.
Two cures were done: better thermal insulation in the fuel system from boost pump to engine-driven fuel injection pump, and better and more lines between header tanks and main tanks, with a fwd and aft tank feed line plus the vapour collection “chimney” direct to the upper part of the tank, with check valve included to ensure it is not filled with flow-impeding liquid fuel. The resulting system has one of the best unusable fuel quantities in the industry: 0.5 USG in a 45 USG tank: ie one way or another if there is some fuel in the tank , except in extreme attitudes, it will find its way down to the header tank. All T/P210’s I have seen have had this mod incorporated.
From 1982 aprox, Cessna had had enough experience to consider the vapour-lock issue tackled on 210’s and that led them to be brave enough to introduce the more “user-friendly” and thus safer “Both” position, doing away with fuel mismanagement accidents, but slightly increasing unusable fuel, as it has a single header tank post-selector valve, instead of the dual pre-selector headers on the earlier models.
So think twice or even better three times whenever designing or introducing changes in any fuel system!
