206L-1 fuel system

[albatross]

Anyone have a good schematic and/or tutorial of the 206L-1 fuel indicating and low fuel level warning system for a Bell 206L-1?
Can’t find one on line.
Just having a very minor friendly debate with a friend and we have agreed to disagree on a few very minor, obscure points.
We do agree that if the darn light comes on “Plan to Land soon as possible and within minutes ” while avoiding violent Aerobatic maneuvers is the way to go.
Thanks.

As an aside …Many years ago : Had a guy walk into a tent one foggy day and tell me he was glad to be there because the “Low fuel light” had come on. He was flying an old 206 A converted to a 206B ….took him out to the aircraft and said “show me”. Master on fuel valve on Pump CB in humm…Boost pump warning light on. Gauge bouncing on zero…He was shocked to learn this was not a “Low Fuel” warning light and that he was about to flame out. Lucky guy because he got to the camp by flying down a very fast, very cold river at 50 feet.

Another bright spark in a 206B having deviated due Wx and at a very low fuel state had the boost pump light come on so did the right thing and landed beside a road less than 1/2 a mile from the hangar. However when he landed the light went out due to the change in attitude so he decided to avoid the embarrassment of walking or hitching a ride to the hangar for a couple of jerry cans of fuel and try to get to the hangar. He picked it up and rotated forward …”beep, beep, Crash, Bang” …aircraft on her side in the ditch. Fortunately he wasn’t too badly injured. The boss was far from happy. Well, at least it was easy to get the aircraft out of the ditch and off to the rebuilders for some TLC.

[SASless]

Oh....what an interesting thread we could have telling those kinds of stories.....leaving the guilty un-named of course!:ok:


.

[nomorehelosforme]

Oh....what an interesting thread we could have telling those kinds of stories.....leaving the guilty un-named of course!:ok:


.

SAS,

Certainly could be interesting, I’m sure sure some of those stories would send shivers down our spines.

[Salusa]

Here you go.

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/636x576/206l1_fuel_17d367b3990fc057183d0e6068e1ac005688ad9f.jpg

[RVDT]

A long time ago in a land far far away.........................

Get your mechs to give you a heads up as there are a few pitfalls and consult all the Safety Notices and Bulletins. The issues have probably been modified out by now but worth knowing if things don't look right they probably aren't.
Not as benign as a 206B.

[paco]

From The Bell 206 Book:

As fuel to the engine can only come from the main tank, a problem in the transfer mechanism (usually from contamination) can mean fuel being trapped and unusable in the front tanks. Cockpit indications are fuel quantity and pressure gauges, 2 boost pump warning lights and a fuel low light. The quantity gauge derives its signal from 3 transmitters, one being in the forward tank, so it will always read total fuel available, but, as the Fuel Low probe is only in the main tank, you can get a fuel low indication with an apparently plentiful fuel load. In fact, when the fuel transfer valves are stuck open (a grain of sand will do), the engine will quit at 200 lbs, or even as high as 240 lbs (from pilot experience).
If you remember nothing else about a LongRanger fuel system, remember this…………
WHATEVER THE FUEL QUANTITY INDICATION -
IF THE FUEL LOW LIGHT ILLUMINATES:
BELIEVE IT,
LAND,
AND CONTACT AN ENGINEER

[albatross]

Thanks for the replies.
Where is the switch/probe in the aft tank of a 206L that activates the low fuel light? Is it located on the lower fuel probe?
Strangely this all started in a discussion about the fuel probe and light on the early 350D Astars. The light would come on when the float got very near the bottom of the probe and touched a switch but we had problems with the float sticking in the tube and giving a false high fuel indication…. just to add fun to events the float was now stuck and so would not descend and activate the light. Not very redundant. We never had anyone run out of fuel and discovered the problem when some observant fellow noticed the level not going down and then suddenly “ losing” 10% when the float became unstuck. Good catch as we were dealing with other serious problems with this new machine.

We did have a very senior pilot run a 206L out of fuel when he had a transfer failure and ignored the light. The auto was a thing of beauty into a nasty confined area with no damage …..the Boss, however, was not impressed, walked into the crowded office, handed him a Timex watch, turned around and walked out without saying a word. Lesson learned. ( nobody dared laugh or even crack a smile in the Senior Pilot’s presence but once we left the office and got out of earshot it took a couple of minutes to get ourselves under control.) The fuel system became a big subject with SP when he was training or checking anyone for a considerable time thereafter.

[Ascend Charlie]

Because the right front cell doesn't have a quantity probe, the reading from the left cell is doubled. So, if there is some problem getting fuel out of the left cell, you can get a false "high" reading for the fuel still in the front, even if the right cell is nearly empty. A vague memory is tickling the back of my brain about this, but it was 30 years ago and turned out to be just something that I had to tell the maintenance people about before it became a problem.

[wrench1]

Where is the switch/probe in the aft tank of a 206L that activates the low fuel light?
The separate low level switch is mounted on the boost pump panel next to the sump valve.

[albatross]

The separate low level switch is mounted on the boost pump panel next to the sump valve.
Thank you Wrench 1. Just the information I was seeking.
Another minor piece of trivia about which a lot of folks are unaware: The left boost pump is hot wired to the Batt. so if you get a “Batt Warm/ Hot indication and wish to isolate the Battery not only do you have to place the “Batt” switch in the OFF position but you also have pull the left hand boost pump C/B in order to totally isolate Mr.Battery.
Gawd- some of the stuff you remember even 30 years later. Last time I had the pleasure of flying an L was 1992. Always liked that aircraft.

[Devil 49]

Thank you Wrench 1. Just the information I was seeking.
Another minor piece of trivia about which a lot of folks are unaware: The left boost pump is hot wired to the Batt. so if you get a “Batt Warm/ Hot indication and wish to isolate the Battery not only do you have to place the “Batt” switch in the OFF position but you also have pull the left hand boost pump C/B in order to totally isolate Mr.Battery.
Gawd- some of the stuff you remember even 30 years later. Last time I had the pleasure of flying an L was 1992. Always liked that aircraft.

I had a couple days in the Gulf of Mexico in a straight 206L. Nice bird if you're empty, fast, for a 206, but weak to pathetic if you gotta carry anything.

[Chock Puller]

Bell made fuel systems interesting in some of their products.

The 412 was very interesting as well with some a lot of numbers to remember when it came to unusable fuel during problems.

[Salusa]

Bell made fuel systems interesting in some of their products.

The 412 was very interesting as well with some a lot of numbers to remember when it came to unusable fuel during problems.

Probably the most complicated Fuel System I have seen on a helicopter.

I can imagine some design engineer waking up one morning ….. "I have an idea. Lets squeeze a fuel cell into every spare space we can find throughout the airframe and interconnect them somehow".

[RVDT]

Might be all BS but I think if one of the check valves that are at the low point didn't close, as one pump was stronger than the other, fuel would circulate back through the open check valve rather than operate the ejector function.

I think the regular test was to have a fuel quantity lower than the exit height to the main tank from the ejector outlet and run the aircraft up to 100% on the ground with the boost pumps off and if the check valve wasn't working it would draw air back the through the ejector exit which was above the fuel level and it would flame out! If so, time to clean the check valves!

Seem to remember it being done pretty regularly back in the day in a land far away with questionable fuel and was more than 30 years ago!

[albatross]

I had a couple days in the Gulf of Mexico in a straight 206L. Nice bird if you're empty, fast, for a 206, but weak to pathetic if you gotta carry anything.

They could be challenging LOL You could be limited in cruise as to how much Q you could pull before you would be near MCP temp.

Ever use the “Water Alcohol Injection System”. That could be “Fun”

My “Lots of Danger Ranger” L time is pretty evenly divided between the L and L-1.
The 206 was humorously referred to as the “Death Ranger” An Astar was a “Death Star”, “DisAstar” or “Falling Star”, a 500 was a “Boiled Egg with a Hard On” . Hey …stuck in a tent or trailer pre-internet and no phone for 6-8 weeks or more at a time we were easily amused.

A straight L at 1000ASL and -30C was great. No problem getting 100%Q and the airframe was lighter than an L-1
I vaguely recall that you started to temp out around +25 or 30C at 1000 ASL. Having an over spec engine was a good thing and most of ours were well over.
Temps in that area varied between -45C in Winter and +35 in Summer. Fun Daze.

I once flew a 206L-1 750 hard working hours in one year with 1, yes, 1 AOG snag. which required 20 minutes to fix. She was a wonder machine. I still think fondly of her. We had some truly marvellous Engineers.

Anyhow Thanks to Everyone for the help.
Cheers
Albatross ( my boss once said, with an exasperated smile, during one of our frequent friendly debates: ”Sometimes you can be ‘The Albatross hanging around my neck’ !” )

[RVDT]

I once flew a 206L-1 750 hard working hours in one year with 1, yes, 1 AOG snag. which required 20 minutes to fix. She was a wonder machine. I still think fondly of her. We had some truly marvellous Engineers.

Straight L-1's had an engine called a "boat anchor" - C-28.

L-1 C30 with "enhamced" MGB was the pick of course (pre L-4). Had 3 on seismic, reduced to 2 as someone dropped a tree on one, of the remaining 2 only one had the enhanced MGB. That one was on drills all the time and I think we put 2400 hours on it in 12 months. Hard machines and we were operating at up to ~3000' but sometimes 45 degrees C!

[Ascend Charlie]

We had an original L, with the C-20 and water methanol. It worked really well, we acknowledged its limits and got 12,000 hours out of it, before a new owner put a junior pilot into it and he flew the new owner into a low cloud and came out vertical. Splat.

The 206L flew faster than its shedmate the 206B, was far smoother with the Nodamatic suspension, and for the same operating costs, we got 2 more bums on the tourist seats.

[albatross]

We had an original L, with the C-20 and water methanol. It worked really well, we acknowledged its limits and got 12,000 hours out of it, before a new owner put a junior pilot into it and he flew the new owner into a low cloud and came out vertical. Splat.

The 206L flew faster than its shedmate the 206B, was far smoother with the Nodamatic suspension, and for the same operating costs, we got 2 more bums on the tourist seats.

We had one straight L in our fleet with no particle separator, no hook, no HF ant. Low skids with fairings only used for “executive stuff” around the city. ( felt very strange to have to wear black shoes, blue pants, white shirt with bars and a decent haircut instead of bush boots, jeans, wool shirt, Jet B Parka and a hair cut that resembled a sheep badly in need of shearing ).
Always hangared, beautiful paint job, washed, waxed, track and balanced to death. She was very fast and fun to fly instead of the particle separator, high skid gear with skis, cargo hook, sling mirror, FM ant, sand eroded blades, Hard working bush beasts we were used to driving up north.
Our bush machines were very well maintained but operating in a harsh environment. Working trucks VS the boss’s gleaming leather interior wunder wagon that had never seen a dirt road.

As to the C-28 on the L-1 after initial teething problems ( mostly with bleed valves and that silly overspeed system ) it was a great engine. Especially when compared to the LTS 101 on the early Astars. We had a lot of big problems up to and including multiple eng failures with those for a myriad of reasons. Ask an old USCG pilot or engineer about early daze with the early LTS 101 equipped “Dolphin”.
“Tis best to remain alert, for you could be hurt, when the engine doth explode!”

[212man]

WHATEVER THE FUEL QUANTITY INDICATION -
IF THE FUEL LOW LIGHT ILLUMINATES:
BELIEVE IT,

I think that’s a general truism, and greater understanding could have saved many lives (Glasgow Police 135 jumps to mind). I know of a 155 that had a flame out after a blocked jet pump left the remaining fuel in the forward left tanks unusable, leaving the crew to believe they had more useable fuel than they did - but a red warning on, of course!

[SASless]

Re the Police Crash....was it the aircraft's fault or just flying longer than the usable fuel allowed as there is always some trapped (non-usable) fuel in a properly functioning fuel system?

[albatross]

I think that’s a general truism, and greater understanding could have saved many lives (Glasgow Police 135 jumps to mind). I know of a 155 that had a flame out after a blocked jet pump left the remaining fuel in the forward left tanks unusable, leaving the crew to believe they had more useable fuel than they did - but a red warning on, of course!

You could get yourself in a very bad spot with the EC 225LP if you did not closely monitor the fuel transfer especially if you had the extra forward external tanks fitted. One of our machines had to drop into Anduki enroute KK to Miri when he still had scads of fuel but not much in the feeder tanks. Of course he was welcomed with open arms and back on his way in minutes to home base to fill out an “interesting and entertaining incident report” that would have won a prize for creative fiction if he had gone with the first draft. “Very nice but I think we can actually prove you were present in body if not mind aboard the aircraft at the time of the alleged incident! Wanna give it another go?”

[Winnie]

Straight L-1's had an engine called a "boat anchor" - C-28.


Also been referred to as the "Allison hand grenade..."