PA-31 down at TCL

Any PA31 drivers care to comment on the fuel system?

How many tanks? What do the boost pumps suck from? What is this 'right emergency fuel pump'?
 
Am i right in assuming that neither engine was running at the time of the accident?

eta, further, as I know next to nothing about CS props. But wouldn't you feather the prop on a dead engine?
 
It's odd that all the fuel pumps apparently were inoperative, neither prop was feathered. Was this plane just in a glide trying to make it to the runway IF both engines somehow were inoperative.
 
mscard88 said:
It's odd that all the fuel pumps apparently were inoperative, neither prop was feathered. Was this plane just in a glide trying to make it to the runway IF both engines somehow were inoperative.
Click to expand...
What's sad is that they ended up 1600' short of the runway. Probably would have made it if he had feathered the props, assuming the engines weren't producing power.
 
Mike Smith said:
Am i right in assuming that neither engine was running at the time of the accident?

eta, further, as I know next to nothing about CS props. But wouldn't you feather the prop on a dead engine?
Click to expand...
It is hard to tell for certain based on the info. Usually the report will note what specific damage to the props that is observed which will indicate whether the engines were producing power at impact. It would seem that based on the fuel pump reports, the engines weren't making power, but hard to say for certain.
 
You say the report stated that the pumps were working? Might have missed it but all I read was the pilot reported losing a fuel pump, and then the other fuel pump. Topped off so fuel should have sufficient unless the engines were burning very rich. Weird because I was watching a Lynyrd Skynyrd documentary and their crash was because of a rich engine consuming all the fuel. I'm wondering if it's something along those lines? Fuel contamination seems unlikely if they flew that far. Did the pilot not switch the tanks correctly and crashed with usable fuel? And not feather the props? I don't have any Navaho time so maybe someone will on here.
 
mscard88 said:
You say the report stated that the pumps were working?
Click to expand...
If you are referring to me, no, I said the report stated they retained the fuel pumps for further examination. There was also no mention about fuel pump switch position or tank selector position.

But what I found odd was there was no mention of recovering/retaining a left boost pump.
 
Fearless Tower said:
If you are referring to me, no, I said the report stated they retained the fuel pumps for further examination. There was also no mention about fuel pump switch position or tank selector position.

But what I found odd was there was no mention of recovering/retaining a left boost pump.
Click to expand...

OK, sorry, misunderstood. I'll see if I can find a fuel system schematic on it.
 
mscard88 said:
Might have missed it but all I read was the pilot reported losing a fuel pump, and then the other fuel pump.
Click to expand...
That is correct and why I'm curious about the fuel system. It is possible that he had plenty of fuel on board, but couldn't access it.

In some airplanes (my Beech for example) you have electric boost pumps that only suck from the mains. So if you are sucking from an aux tank and lose the engine driven pump, you will lose the engine unless you quickly shift the the main and turn the boost on.

Another possibility is if he previously ran a tank dry. There might have been air in the line and even though he topped it off, he might have experienced suction problems on the next leg.

But all this is general speculation without knowing about the PA31 specifics.
 
mscard88 said:
Wow, here's something I found with another Navajo. Has the fuel system in there as well.

https://assets.publishing.service.g...5274a1314000627/PA_31_Navajo__N80HF_04-11.pdf

I only see 2 electric and 2 engine driven pumps.

HOWEVER the Navajo at TCL may have been a different model or had a fuel system modification.
Click to expand...

I am thinking (speculating) that the issue wasn't multiple fuel pump failures, if both engine driven pumps failed, very unlikely in a short period, the odds of BOTH electric pumps failing on the same flight has got to be .000000000000000000000001% this is stuff even the most evil sim instructor won't throw at you. It is a terribly tragic situation for the 11 kids, but in my limited experience, I have never heard of 4 out 4 fuel pumps failing on a given flight. Could he have possibly turned on the wrong electric pump and flooded the engine with the good mechanical pump causing it to quit? I just don't have a good theory.
 
any chance of dirty fuel? sand/dirt etc in the fuel leading to multiple pump failures? USUAL DISCLAIMER: eman1200 doesn't know jack squat about twins and their fuel systems, just a randomly wild guess.
 
I agree 747JB, that it's highly unlikely that ALL the fuel pumps quit all at once. Speculating on my part here, but could be mismanagement of the fuel system, fuel contamination a possibility but unlikely as they were probably an hour+ into the flight, and there was a fire which suggests there was fuel onboard. Another is failing to feather the props is another concern I'm wondering about. Affects the glide distance. I live about 40-50 miles from TCL and there are a few airports south of TCL but it's pretty sparse. Don't know when he notified ATC of his problems and thinking ATC could have found him something closer. Sad indeed for those children.
 
Last edited:
eman1200 said:
any chance of dirty fuel? sand/dirt etc in the fuel leading to multiple pump failures? USUAL DISCLAIMER: eman1200 doesn't know jack squat about twins and their fuel systems, just a randomly wild guess.
Click to expand...

It's a possibility for sure.
 
N747JB said:
I am thinking (speculating) that the issue wasn't multiple fuel pump failures, if both engine driven pumps failed, very unlikely in a short period, the odds of BOTH electric pumps failing on the same flight has got to be .000000000000000000000001% this is stuff even the most evil sim instructor won't throw at you. It is a terribly tragic situation for the 11 kids, but in my limited experience, I have never heard of 4 out 4 fuel pumps failing on a given flight. Could he have possibly turned on the wrong electric pump and flooded the engine with the good mechanical pump causing it to quit? I just don't have a good theory.
Click to expand...
Agree. It is worth noting that the pilot had less than 50 hrs in type.

I don't point that out to be judgmental, but I myself have experienced a couple of surprise fuel and other system issues in my Beech 18 in the 40 hrs I've flown the airplane. I've been very fortunate that those learning moments didn't occur during critical phases of flight.
 
eman1200 said:
any chance of dirty fuel? sand/dirt etc in the fuel leading to multiple pump failures? USUAL DISCLAIMER: eman1200 doesn't know jack squat about twins and their fuel systems, just a randomly wild guess.
Click to expand...

Dude. They run on food. Take them to dinner.
 
The higher HP Navajos (325hp and 350hp) have three pumps per side. There is what I will call a header pump that is on whenever the master switch is on. That feeds the electric fuel pump that is on for takeoff and landing or if the engine driven pump fails. Then there it goes to the engine driven pump.

I will note that if the pilot took off on the mains, climbed to 12,000 and switched to the aux tanks, he started his descent at around the point that he would have exhausted fuel in the aux tanks. Probably he would have gotten a pump failure light just prior to the engine quitting. It is too bad that the preliminary didn't tell us what position the fuel selector valves were in. If they were in the AUX position, it would be highly indicative of the pilot running the aux tanks dry and then because of the warning light, focusing on the pump failure and not switching his tanks because he didn't really understand the system and under stress it didn't occur to him that he should switch tanks.
 
Ok, I fly a PA-31-350. The Panther conversion is different engines, but the systems are similar.

Fuel pumps. 3 per engine.

1. Low Pressure Boost Pumps.
Each engine is fitted with a low pressure boost pump which provides 10PSI of positive pressure from the moment the master is turned on.
This 10PSI can be used for priming but is primarily in place to provide a constant flow of fuel to the high pressure engine driven fuel pump and thus prevent cavitation. Sometimes called the altitude pump.

2.High Pressure Boost Pump. Engine driven.

A positive displacement VANE type pump. High pressure with greater capacity than engine demand.
Pump outlet fuel pressure passes through an orifice affected by turbo output pressure and before entering relief valve chamber thus making pump delivery pressure proportional to engine speed.

3. Emergency pump. Used for every take off and landing. Also used if one of the other pumps fail. The emergency fuel pump should be used to get you to the destination or alternate airport. Not to be used in place of the low pressure boost pump. In other words, get it fixed before the next take off.

I have lost a low pressure boost pump at cruise. The engine started surging as if the tank was running dry. Turning on the emergency pump stopped the surging, and I made my destination without any more problem.

Fuel tanks. Two per wing. Inboards are the main tanks which are used for take off and landing. The outboards are used in cruise. The inboards hold 53 usable per side, and the outboards hold 36 usable per side. (standard tanks for the plane I fly)

The fuel tank selector valves are located at the bottom of the throttle quadrant. Each wing has its own control, which are outboard, off and inboard. To select a different position, there is a pin type lock that must be lifted, then the lever can be moved to the desired tank. Make sure the pin locks into the hole of the new position. I watch the fuel pressure gauge for a few seconds to make sure there is no loss of fuel pressure. There is a cross feed system on the fuel system.

Cowl flaps. The cowl flaps are huge. The plane WILL NOT hold altitude with one engine inoperative with the cowl flaps open at or near max gross weight.
 
Last edited:
Kristin said:
I will note that if the pilot took off on the mains, climbed to 12,000 and switched to the aux tanks, he started his descent at around the point that he would have exhausted fuel in the aux tanks. Probably he would have gotten a pump failure light just prior to the engine quitting. It is too bad that the preliminary didn't tell us what position the fuel selector valves were in. If they were in the AUX position, it would be highly indicative of the pilot running the aux tanks dry and then because of the warning light, focusing on the pump failure and not switching his tanks because he didn't really understand the system and under stress it didn't occur to him that he should switch tanks.
Click to expand...

Based on the description of the events and my limited PA-31 experience, I had the same thoughts.
 
Thanks Kristan and Zeldman. Mismanagement of the fuel system would not surprise me to be the cause. Especially since there was quite a fire after impact.

Question for you two. Kisimmee to TCL, would that be indicative of proper management of the fuel selector, ie mains for TO then switch to aux tanks, and then south of TCL running the aux's dry?
 
Last edited:
mscard88 said:
Thanks Kristan and Zeldman. Mismanagement of the fuel system would not surprise me to be the cause. Especially since there was quite a fire after impact.

Question for you two. Kisimmee to TCL, would that be indicative of proper management of the fuel selector, ie mains for TO then switch to aux tanks, and then south of TCL running the aux's dry?
Click to expand...

All except the part about running the tanks dry is proper. Especially with passengers. They hate that. I don't know whether he had a totalizer but should have had a good idea what the burn rate was and set a time or whatever to remind him to switch tanks. For this flight, which was not to the limits of fuel, I probably would only have taken an hour and a half or so off the aux tanks leaving probably 10 or so gallons in it. No point in cutting it super close.

Regardless, if you run a tank dry, boost pump on and switch to the mains will get a restart, at least I haven't had an issue with it.
 
Thanks Kristin, and I agree about not running a tank completely dry. I was just wondering if that pilot operated pretty much as you say, and Zeldman, if the aux tank would be dry around where the pilot began to experience his problems.
 
mscard88 said:
Thanks Kristin, and I agree about not running a tank completely dry. I was just wondering if that pilot operated pretty much as you say, and Zeldman, if the aux tank would be dry around where the pilot began to experience his problems.
Click to expand...

Just to be clear, I am not morally opposed to running a tank dry per se. I am morally opposed to scaring the daylights out of the passengers. :) All by myself in my Twinkie, I have run tanks dry when running out to the limits of fuel capacity.

It is impossible guess for sure that he ran an aux dry, but it is certainly within the realm given the aux tank's capacity, time in the air, and likely fuel burn.
 
Thanks Kristin, that's what I was curious about.
 
Kristin said:
Just to be clear, I am not morally opposed to running a tank dry per se. I am morally opposed to scaring the daylights out of the passengers. :) All by myself in my Twinkie, I have run tanks dry when running out to the limits of fuel capacity.

It is impossible guess for sure that he ran an aux dry, but it is certainly within the realm given the aux tank's capacity, time in the air, and likely fuel burn.
Click to expand...
I didn't run the tank dry, it was very close in my 421B, but I switched from aux back to mains and the first one was fine, the second one I switched the wrong way! :eek: From AUX to OFF instead of MAIN, my wife nearly passed out then, she threatened me to never change tanks again!! :mad: OK, dear, I am sorry!! :D
 
Kristin said:
The higher HP Navajos (325hp and 350hp) have three pumps per side. There is what I will call a header pump that is on whenever the master switch is on. That feeds the electric fuel pump that is on for takeoff and landing or if the engine driven pump fails. Then there it goes to the engine driven pump.

I will note that if the pilot took off on the mains, climbed to 12,000 and switched to the aux tanks, he started his descent at around the point that he would have exhausted fuel in the aux tanks. Probably he would have gotten a pump failure light just prior to the engine quitting. It is too bad that the preliminary didn't tell us what position the fuel selector valves were in. If they were in the AUX position, it would be highly indicative of the pilot running the aux tanks dry and then because of the warning light, focusing on the pump failure and not switching his tanks because he didn't really understand the system and under stress it didn't occur to him that he should switch tanks.
Click to expand...
If I had to bet, I would put money on this being the correct explanation. Tip tank Cessna's have a fuel system that isn't intuitive until you get used to it and it sounds like the Navajo has one that is just as complicated to a first time or low time in type pilot. This explains why he thought he had double pump failures.
 
Kristin said:
Just to be clear, I am not morally opposed to running a tank dry per se. I am morally opposed to scaring the daylights out of the passengers. :) All by myself in my Twinkie, I have run tanks dry when running out to the limits of fuel capacity.

It is impossible guess for sure that he ran an aux dry, but it is certainly within the realm given the aux tank's capacity, time in the air, and likely fuel burn.
Click to expand...
IF you run a tank dry in the PA31, and then refill it, can you run into problems with air in the lines?
 
Fearless Tower said:
IF you run a tank dry in the PA31, and then refill it, can you run into problems with air in the lines?
Click to expand...

I wouldn't think so. That's one of the reasons during engine start to run electric pumps, to purge air out right?
 
N747JB said:
If I had to bet, I would put money on this being the correct explanation. Tip tank Cessna's have a fuel system that isn't intuitive until you get used to it and it sounds like the Navajo has one that is just as complicated to a first time or low time in type pilot. This explains why he thought he had double pump failures.
Click to expand...
That was my gut feeling too.

Moving up to the Beech 18 from the very simplistic B55 Baron, I have already found a few surprises in the various systems in my short time in the airplane. I can imagine someone stepping into a Navajo from a smaller twin experiencing similar surprises.
 
N747JB said:
Tip tank Cessna's have a fuel system that isn't intuitive until you get used to it
Click to expand...

You're not kidding - I was a low time guy in a 340 and ran an aux tank dry by accident. The engine stumbled for just a few seconds while I switched tanks, but I'm pretty sure my poor passenger managed to suck the *entire* seat cushion up his ass. Not one of my better moments, but a learning situation for sure.
 
Probably one of the more important (they're all important of course) systems to thoroughly understand on a twin.
 
mscard88 said:
I wouldn't think so. That's one of the reasons during engine start to run electric pumps, to purge air out right?
Click to expand...
But that is assuming you start on the tank you ran dry.

I ask because I have experienced issues in the Beech 18 with sucking from an aux tank that was full of fuel but intentionally run dry on a previous flight. You always start the Twin Beech on the mains (only tanks served by the boost pumps). I was ultimately able to get auction from the auxes, but it took a couple attempts and initially acted like the engines were running out of fuel.
 
Engine driven pump and electric pump for both engines. Concerning air in the line it is normal to run the outboards empty then switch to mains. If you are good you can watch for flow fluctuations and switch before the engine even hic cups. A popular way to manage fuel is to take off (required to be on mains) and climb to altitude. Switch to outboards and empty them then switch back to mains. On mains required for landing. IMO it is highly unlikely to have lost two engine and two boost pumps at the same time. If the tanks (all four) were topped off and he had six adults and luggage that was one heavy plane. I have never seen a CR with a useful load above 800 pounds with full fuel. If it had the Colemill conversion it would have had even less useful load since the crankshaft extensions and the winglets add weight. Not all Colemill conversions of the CR had the 350 HP engines. It will be interesting to see if there was any fuel in the plane when it crashed.
 
I only used the boost pumps to prime (or purge vapor on a hot engine) then turned off pumps for the actual start. Boost pumps back on for take off. Boost pumps were to be used during switching tanks and landing.

Edit: Just to clarify the boost pumps I am referring to are not to be confused with the low pressure pumps that come on when the master is on. The high pressure pumps are pilot controlled and what I refer as boost pumps. they will take the place of the engine driven pumps but, you may be power limited due to altitude.
 
Last edited:
mscard88 said:
Thanks Kristin, and I agree about not running a tank completely dry. I was just wondering if that pilot operated pretty much as you say, and Zeldman, if the aux tank would be dry around where the pilot began to experience his problems.
Click to expand...

I never fill the outboard tanks so I can carry more revenue, but in the Chieftain I fly I would expect about 1.5 hours with topped off outboards and normal cruise settings.

I agree with Kristin, not scaring the holy ned out of the paying passengers is goal #1.

I was flying a C-340 once, and was told there was 5 to 10 gallons of fuel left in the aux tanks, so I switched tanks at cruise. More like 5 to 10 seconds of fuel was left. Last time I listened to the boss....
 
ronnieh said:
It will be interesting to see if there was any fuel in the plane when it crashed.
Click to expand...

Didn't it burn pretty good after hitting? That would suggest fuel in tanks. These videos of crashes run together...
 
May have, not sure, just speculating.
 
Kristin said:
I looked at the photos on Kathyrn's report. That showed a four blade prop, suggesting that it probably had the Colemill Panther conversion. That would have given it 350 hp a side, which will have improved the SE performance. The prop that is shown in the picture either stopped very suddenly so that two of the blades appeared pretty much undamaged, or the engine was seized with the prop not feathered. I have made a note in my calendar to check for a preliminary in a week or so.
Click to expand...

Both fuel pumps failed, and neither prop feathered? Could he had been flying on the boost pumps with inop engine driven pumps? Otherwise wouldn't he have electric pumps to use in case of mechanical pump failure?
 
You must log in or register to reply here.
Back
Top