Navaho Ambulance down short of PWK

Just answer the question yes or no. It shouldnj't be too tough even for you.

Have you personally experienced an in-flight fuel leak in a twin?

Inverted said:
You are clearly making ignorant statements to cause a stir, there is no possible way you are suggesting this.
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Yes I have, have you? You clearly don't know what the hell you are talking about.
 
You can feed each engine off its own tank.
You can feed both engines off ONE tank.
You can feed each engine off the OPPOSITE tank.
You cannot feed an engine off both tanks at once.

Thus, any single fuel leak will be in one system or the other, and cause a loss of fuel on one side only.

So it's certainly possible for a single leak to result in a fuel exhaustion situation in one system, but unless you're feeding both engines off a single tank (and the pilot should know this), you wouldn't have dual flameouts.
 
We'll see who knows what, and it won't take long.

How did you know you had a leak?

Inverted said:
Yes I have, have you? You clearly don't know what the hell you are talking about.
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Do both engines burn fuel at exactly the same rate? On every trip? Every time? Are the tanks always filled to the exact same quantity? Every trip? Every time? Are all ramps absolutely level? Are airplanes always sitting absolutely level when fueled? Do crossfeed systems always work? How often are crossfeed systems sufficiently tested by the crew?

TMetzinger said:
You can feed each engine off its own tank.
You can feed both engines off ONE tank.
You can feed each engine off the OPPOSITE tank.
You cannot feed an engine off both tanks at once.

Thus, any single fuel leak will be in one system or the other, and cause a loss of fuel on one side only.

So it's certainly possible for a single leak to result in a fuel exhaustion situation in one system, but unless you're feeding both engines off a single tank (and the pilot should know this), you wouldn't have dual flameouts.
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wabower said:
We'll see who knows what, and it won't take long.

How did you know you had a leak?
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You have already proved you don't know what the hell you are talking about so keep digging your hole.

And I noticed the fuel imbalance on the gauges. Next question professor?
 
TMetzinger said:
You can feed each engine off its own tank.
You can feed both engines off ONE tank.
You can feed each engine off the OPPOSITE tank.
You cannot feed an engine off both tanks at once.
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(I assume the above to be correct, never flown a navajo)

/scenario
So you are cutting it close to minimums on this haul from GA to Chicago. Weather is forecast good enough that you dont need an alternate. Just short of your destination you loose fuel pressure and subsequently power on one side, so you switch that engine on cross-feed, a little bit of tail-wag the engine roars back to life. Now you are depleting the remaining tank at twice the rate. Your 45min reserve is now 22.5 min. That tank you are now drawing off also fed the heater for the past 3 hrs.....

/end scenario
 
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Pretty amazing how a pilot would continue to blaze the throttles and still burn the same amount of fuel knowing one tank is dry and the other has 22.5min of fuel based on his cruise burn isn't it? Also pretty amazing how he crashed 3 miles away from the destination when that area is littered with probably 20 airports in a 30nm radius.
 
At what point during the flight did this occur?

How long had it been leaking?

How much fuel was missing?

Were the engines fuel-injected Lycomings?

What did you do after noticing the imbalance?





Inverted said:
You have already proved you don't know what the hell you are talking about so keep digging your hole.

And I noticed the fuel imbalance on the gauges. Next question professor?
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wabower said:
At what point during the flight did this occur?

How long had it been leaking?

How much fuel was missing?

Were the engines fuel-injected Lycomings?

What did you do after noticing the imbalance?
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Dude are you kidding? What do I need to prove to you? And no they were PT-6s. I have nothing to prove to you. You can think what you want, I am certainly gonna think what I want about you based on your hair brain comments.
 
It's good to see you have figured out you have no idea how to answer the questions and are now running for cover. If you keep reading maybe you will have learned something by the time this thread runs its course.

BTW, which PT-6 engines were involved? And what should you do if you see a fuel imbalance on the gages?



Inverted said:
Dude are you kidding? What do I need to prove to you? And no they were PT-6s. I have nothing to prove to you. You can think what you want, I am certainly gonna think what I want about you based on your hair brain comments.
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Inverted said:
Pretty amazing how a pilot would continue to blaze the throttles and still burn the same amount of fuel knowing one tank is dry and the other has 22.5min of fuel based on his cruise burn isn't it? Also pretty amazing how he crashed 3 miles away from the destination when that area is littered with probably 20 airports in a 30nm radius.
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In this scenario, the delta in time between engine 1 and 2 failing is mostly dependent on the amount of fuel missing from tank 1.
 
Interesting ****in match...

From my point of view, if you can't trust the fuel flow meter and you can't trust the fuel gauge then you better be flying strictly by time and never past 75% of the fuel you started with... Working for idiots makes the job really tough... You may need to quit if you want to live..

Personally, I have 6 hours of fuel on board... My longest leg ever was 4:20... Anytime the fuel reaches one hour (by timer) it WILL be on the ground - my life, my rule... And my bladder will NOT go 6 hours...

denny-o
 
wabower said:
Have you ever experienced a fuel leak in a twin?
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Not yet, but I have cut my fuel reserves too close and that wasn't a fun experience.:mad2: My point is the flight to Jesup used almost all the fuel available, or at least what we think was available, 165 gallons added at Jesup. He should have known at that point the gauges, or fuel flow meter either were or weren't accurate. It doesn't take a rocket surgeon to divide the amount of fuel loaded by the time flown to see if you are burning what you think you are burning. Even without a leak, I think he would have been below the reserve amount either required by the company or the FAA.
We may never know, especially if the co-pilot doesn't talk, but I'm betting on no leak.
 
weilke said:
(I assume the above to be correct, never flown a navajo)

/scenario
So you are cutting it close to minimums on this haul from GA to Chicago. Weather is forecast good enough that you dont need an alternate. Just short of your destination you loose fuel pressure and subsequently power on one side, so you switch that engine on cross-feed, a little bit of tail-wag the engine roars back to life. Now you are depleting the remaining tank at twice the rate. Your 45m
in reserve is now 22.5 min. That tank you are now drawing off also fed the heater for the past 3 hrs.....

/end scenario
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All reasonable... and shouldn't be a surprise to the aircraft pilot.

The situation I was pointing out as unlikely was:
Twin flying with a single fuel leak.
Both engines fail at the same time.
The cause of the failure is the fuel leak, and until the failure that leak was undetectible by the pilot.
 
TMetzinger said:
All reasonable... and shouldn't be a surprise to the aircraft pilot.
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The suprise is if you have less fuel than you thought in the second tank.

The situation I was pointing out as unlikely was:
Twin flying with a single fuel leak.
Both engines fail at the same time.
The cause of the failure is the fuel leak, and until the failure that leak was undetectible by the pilot.
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Quite unlikely. If a single fuel leak caused this, a dual engine failure requires pilot input, tank switching, a couple of swear words etc.
 
weilke said:
The suprise is if you have less fuel than you thought in the second tank.
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Short of an actual leak, a proficient pilot shouldn't ever have less fuel than he expects in his tank(s). By that I mean being surprised, which to me means more than 30 minutes difference between what the pilot THINKS he has and what he actually has.

weilke said:
Quite unlikely. If a single fuel leak caused this, a dual engine failure requires pilot input, tank switching, a couple of swear words etc.
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Yes, that was my point
 
Inverted said:
Also pretty amazing how he crashed 3 miles away from the destination when that area is littered with probably 20 airports in a 30nm radius.
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If you look at Flightaware's "Live Flight Tracker" he had been vectored to ride the shoreline, so there were NOT a ton of airports nearby. Being over one of the great lakes when the engines sputter to a halt is a bad day.

http://flightaware.com/live/flight/N59773

Looking at the "Flight Track Log" and the minute by minute data, there is an odd increase in speed about 3 minutes prior to the crash. The very next minute, the descent rate increases by a lot.

http://flightaware.com/live/flight/N59773/history/20111128/2308Z/KJES/KPWK/tracklog

Notice that earlier in the flight they were at 10,000'. Then they stepped down to 8K, 7K and finally 6K for much of the trip. I'm wondering if this has something to do with the fuel consumption rates.

Also, notice that towards the end they levelled off at 4K and 3K while skirting the shoreline. Then he abruptly turns west and starts descending. I think he turned SE at the very end once he broke out of the clouds and saw he wasn't going to make PWK. Just a guess on my part.
 
Morne said:
Notice that earlier in the flight they were at 10,000'. Then they stepped down to 8K, 7K and finally 6K for much of the trip. I'm wondering if this has something to do with the fuel consumption rates.
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The fuel consumption on the Navajos I fly is pretty much indifferent to altitude, until you get up above 12k. At 14k I'll burn a bit more fuel, but I wouldn't be doing that altitude on a Lifeguard flight. Plus, the TAS will be faster as you go higher (to a point) as the engines are turbocharged. More likely there were other reasons.
 
Is it your testimony, sir, that detectible and detected should be considered as synonomous?

How does a pilot detect a fuel leak?

How does he know it's a quantity problem vs an indication problem?

How does he know when it started?

How does he determine the source?

How does he determine the rate?

Can he predict whether the rate will change prior exhaustion?

Are aircraft fuel systems designed so that the engines are supplied with more fuel than they need to operate and the surplus fuel is returned to the tank(s)?

Could a leak occur at a time during a flight when the combined leak and burn rate would exhaust available fuel prior to the airport of intended destination?





TMetzinger said:
All reasonable... and shouldn't be a surprise to the aircraft pilot.

The situation I was pointing out as unlikely was:
Twin flying with a single fuel leak.
Both engines fail at the same time.
The cause of the failure is the fuel leak, and until the failure that leak was undetectible by the pilot.
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wabower said:
Is it your testimony, sir, that detectible and detected should be considered as synonomous?
If it's detectible by the pilot, the pilot should detect it. That's not saying it IS detectible.

How does a pilot detect a fuel leak?
Having a mismatch between the fuel gauges and the fuel flow totalizer. I admit that this requires something like the G1000 or other systems where you have two independent systems - one measuring fuel level in the tanks, and the other showing the fuel delivered to the engines. But even with just gauges, if your flight plan shows you should have exhausted half your fuel, and your fuel gauges show you've exhausted 5/8 or 3/4, then you should detect that anomaly.

How does he know it's a quantity problem vs an indication problem?
He may not, but if he's prudent, he'll take action as soon as he gets the "I may have a problem" feeling.

How does he know when it started?
He doesn't. So he lands as soon as practicable.

How does he determine the source?
On the ground.

How does he determine the rate?
If he detects it early enough he can monitor. If he catches it 5 minutes before exhaustion, he probably can't.

Can he predict whether the rate will change prior exhaustion?
Probably not. But fuel disappearing when you don't know why, is reason enough to discontinue the flight.


Are aircraft fuel systems designed so that the engines are supplied with more fuel than they need to operate and the surplus fuel is returned to the tank(s)?
I believe some might be, but don't know. I know of no system designed to throw fuel overboard, so normal operations should show fuel disappearing at a rate that matches up with the engines specific fuel burn for the power setting.

Could a leak occur at a time during a flight when the combined leak and burn rate would exhaust available fuel prior to the airport of intended destination?
Absolutely. That's why you monitor your gauges and totalizer during the flight and if they don't agree with your flight plan, or each other, you treat it like a problem, and either figure it out to the point where you are certain you know what's going on and have enough fuel to continue, or you don't press on.
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Now, none of that was really relevant to what I've said. All I've said is that a single leak in a twin would not cause a symmetric engine failure in the "normal" flight configuration where each engine is feeding off it's own tank at pretty much the same rate. Whichever side has the leak is going to exhaust first. I'm not commenting on this accident, just the way twins have fuel systems set up so that a leak on one side won't drain fuel from the other.

If you fly in the winter a lot in a light twin with a gas-powered heater, you can expect your tanks to become unbalanced because the heater will draw fuel from one tank and so the drain on that tank is higher. To compensate, the pilot will crossfeed the engine from the other tank for a bit (maybe 10 minutes out of an hour) so that the drain from both tanks matches up.

I've written a scenario for the Redbird where we simulate a fuel cap left off, and the pilot's expected to detect the fact that his fuel totalizer shows he's burned 20 of 88 gallons but his fuel gauges are showing half fuel. This is in a single where a leak can affect both tanks.
Still working on getting the sim to let the instructor simulate the leak, but it should be a good exercise. A good pilot cross checks the systems information the same way he cross-checks his instruments.
 
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If both wing tanks are exhausted in an Aerostar, how many tanks are available to feed both engines?

TMetzinger said:
Now, none of that was really relevant to what I've said. All I've said is that a single leak in a twin would not cause a symmetric engine failure in the "normal" flight configuration where each engine is feeding off it's own tank at pretty much the same rate. Whichever side has the leak is going to exhaust first. I'm not commenting on this accident, just the way twins have fuel systems set up so that a leak on one side won't drain fuel from the other.

If you fly in the winter a lot in a light twin with a gas-powered heater, you can expect your tanks to become unbalanced because the heater will draw fuel from one tank and so the drain on that tank is higher. To compensate, the pilot will crossfeed the engine from the other tank for a bit (maybe 10 minutes out of an hour) so that the drain from both tanks matches up.

I've written a scenario for the Redbird where we simulate a fuel cap left off, and the pilot's expected to detect the fact that his fuel totalizer shows he's burned 20 of 88 gallons but his fuel gauges are showing half fuel. This is in a single where a leak can affect both tanks.
Still working on getting the sim to let the instructor simulate the leak, but it should be a good exercise. A good pilot cross checks the systems information the same way he cross-checks his instruments.
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wabower said:
If both wing tanks are exhausted in an Aerostar, how many tanks are available to feed both engines?
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Don't know the aerostar system, but not sure it matters. tell me how both sides got simultaneously exhausted by a single leak, please. That's the ONLY point I'm addressing.

Obviously, when the fuel's gone, it's gone. But unless you have symmetrical losses on both sides, you're not gonna run out on both sides at the same time.

Easiest way to run out of fuel on both engines at the same time is to be a knucklehead and fly longer than you should have, or at higher power settings and not monitor your fuel properly.
 
The tanks were emptied by use, not by a leak. The leak started after the tanks were empty.

TMetzinger said:
First, tell me how both tanks got exhausted by a single leak, please. That's the ONLY point I'm addressing.

Obviously, when the fuel's gone, it's gone. But unless you have symmetrical losses on both sides, you're not gonna run out on both sides at the same time.

Easiest way to run out of fuel on both engines at the same time is to be a knucklehead and fly longer than you should have, or at higher power settings.
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You're not thinking. I asked how the pilot determines the source of the leak, and your answer was "on the ground." That's a good-enough answer if the airplane happens to arrive on the ground at an airport and in one piece, but the inescapable fact is that they don't all turn out that way.
Now you're assuming the only source of a fuel leak must be from one of the tanks.

What's wrong with this picture? Here's a hint--we're discussing fuel leaks, not fuel tank leaks.

And BTW, your prior answer about comparing the totalizer quantity to the tank quantity is a little weak, given the makeup of the GA fleet.

TMetzinger said:
I don't understand. If the tanks are empty, how does a leak in one of those tanks affect the fuel remaining in other tanks?
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wabower said:
And BTW, your prior answer about comparing the totalizer quantity to the tank quantity is a little weak, given the makeup of the GA fleet.
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Well, this plane was used for revenue service. It would be reasonable to expect that such a plane has a digital fuel flow gauge and a fuel totalizer. Unfortunately, some operators seem to work under the premise that the fewer pieces of equipment they install in their revenue plane, the fewer things can break and they are generally cheap, also there is no FAR that requires an operator to be 'reasonable'.

Still wouldn't detect a leak in the tank, the plumbing or somewhere between the fuel servo and the injectors (the kind that paints the engine compartment a nice rich blue ;) ).
 
Morne said:
If you look at Flightaware's "Live Flight Tracker" he had been vectored to ride the shoreline, so there were NOT a ton of airports nearby. Being over one of the great lakes when the engines sputter to a halt is a bad day.

http://flightaware.com/live/flight/N59773
..t.
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That's wild. That's about the route I'd take just sneaking in VFR between GYY and MDW's airspace. I guess the fine, fine., folks at C90 send all flibs that way to keep them out of their hair. He did almost overfly UGN on the north lakeshore.
 
I see where Wayne is going with this and it's worried my at times. Certainly, there could be a fuel leak that would be difficult to detect until an engine sputtered. I've flown in a club plane (not the current club I'm in) with inaccurate fuel flow gauges and the fuel gauges didn't show empty when they should have. Bad stuff!
Lots of variables: I consistently burn more fuel on the left side; some planes return excess fuel to one tank not each main; as has been said, I've had fuel rush out of one tank on the ramp after being filled when the other was down visibly, etc. I think risk is higher when one flies different planes with different crews; it's just difficult to know all the inconsistencies of each piece of equipment on each plane as well as one could know one they consistently flew.

This may or may not relate to this accident, but let me cite something. If you're worried about an engine failure, this is interesting.

Best,

Dave
========================================
At ABS this year, Tom Rosen mentioned this statistic:

91 % - 9 out of 10 – ENGINE FAILURES were FUEL RELATED in the 10 years ending last year

Tom Turner gave me that stat and he used it again in his seminar. Amazing isn't it.
 
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Dave Siciliano said:
91 % - 9 out of 10 – ENGINE FAILURES were FUEL RELATED in the 10 years ending last year

Tom Turner gave me that stat and he used it again in his seminar. Amazing isn't it.
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That is the only area where TAAs have a better safety record than steam-gauge planes.
 
As we all know, FF gauges only have to be accurate when they indicate empty. Quite a bit of fuel could be lost before the gauge might drop in a manner that caught the pilot's attention. Even with a digital FF gauge like I have (Shadin), it won't know what's lost before it gets to it; it just shows what was programed in less what was used. I have analog FF gauges that are fairly accurate, but they don't know how much fuel might be lost before it gets to them.

If range was pushed, it would certainly seem probably one engine would be lost shortly before the other. With just my normal fuel burn indifference, I could see seven to ten minutes difference, but if I switched to cross feed, that would certainly change things.

Good food for thought.

Best,

Dave
 
Bingo. Consider the following scenario.

A Cessna 421C (or whatever) departs on a X/C trip with adequate fuel for destination plus alternate plus reserves. The pilot's SOP is to check all engine and systems gages at 20 minute intervals. With roughly an hour and 20 minutes remaining in the trip, the pilot notices that the left tank is indicating lower than the right tank, but not alarmingly so. This appears to be different from what he's been seeing during the trip, but not enough to ring the alarm bell.

The pilot might assume an indication error, or maybe an impending failure in a sending unit, or that the left tank wasn't completely filled at takeoff and the gage error has just become noticeable as the quantity sensors have become more sensitive at reduced fuel load, or that the engine is burning a bit more, or the mixtures weren't set to match or whatever. He knows that he's carrying more reserve fuel than necessary, and diverting to the alternate won't be necessary since destination weather is good.

At the next 20-minute check, however, he notices a significant imbalance, and decides that he just might have a fuel leak after all.

Being a good student of the game, he quickly calculates whether the fuel remaining in the right tank will be sufficient to provide fuel to both engines for the remainder of the trip, if in fact the left tank runs dry, and is comforted to know that he's still well within acceptable fuel margins.

The fuel quantity in the left tank continues to decine, and the left engine sputters about 20 minutes later. The pilot immediately switches to crossfeed which in turn provides the left engine with fuel from the right tank, and is somewhat relieved to know that he won't have to worry about the leak any longer since the left tank is out of the picture, the system is working normally and things are good.

At the next 20 minute check he notices that the fuel gage for the RH tank is dropping a bit more quickly than he anticipated, but since he's now close to his destination and his prior calculation showed that he was fat on fuel, he knows that he is good to go and will reach his destination safely.

About 5 miles from destination, both engines quit simultaneously and the Eagle starts gliding to earth. The pilot finds that he is miraculously perfectly aligned with a recently harvested bean field and lands between the rows with no damage to the airplane or pax, and the only casualty is his underwear. Where will the leak be found when the mechanics show up?





weilke said:
Well, this plane was used for revenue service. It would be reasonable to expect that such a plane has a digital fuel flow gauge and a fuel totalizer. Unfortunately, some operators seem to work under the premise that the fewer pieces of equipment they install in their revenue plane, the fewer things can break and they are generally cheap, also there is no FAR that requires an operator to be 'reasonable'.

Still wouldn't detect a leak in the tank, the plumbing or somewhere between the fuel servo and the injectors (the kind that paints the engine compartment a nice rich blue ;) ).
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Everskyward said:
That would have gone over well...

I didn't have much problem with the "expert". What is said was simplified but more or less the truth. Small airplanes are statistically far more likely to have accidents than airliners and many accidents are due to pilot error.
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Rob Mark is one of the hosts of the "Airplane Geeks" podcast. He's in Paris because he's writing a book on the Air France 447 accident over the Pacific, and there's a conference there on aviation safety.
 
Somewhere ahead of the pump. Some Lyc's have a "D-shaped" fuel line with a history of breaking off at the fitting, but remaining aligned with the hole so that sufficient fuel pressure was available to operate the engine normally, but an undetermined amount was also being pumped overboard around the point of fracture. IOW, the fuel supply was providing sufficient fuel to supply ~three engines when only two were installed. The timing of the fracture, the pilot's awareness of the situation and his ability to properly diagnose the problem (IMO almost impossible) were contributing factors to the resulting accidents or (in my situation) a forced landing at an unintended airport along the route of flight.

weilke said:
In a 421: in the fuel return line.
In a Navajo ?
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