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Fuel Topping?


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What does anyone know about this. It has been discussed at great length at work. And there is debate over fact or myth. Where did this terminology come from? Any input would be great.

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It can mean two different things to me if someone said fuel topping to me.

If it were pilots or operations people I would think it was like Bob said...topping off the tanks via the over wing reciprocals after the SPR had shut off.

If it was the maintenance people, or fellow FE\'s I would maybe think they were talking about the fuel topping governor and doing the fuel topping test during an engine run.

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If your talking about the fuel control fuel topping (103%) it is far from a myth.

From the Lockheed Engine training manual (-7, B model book)

\"A flyweight governor, in the fuel control, limits engine speed to 104.5 to 105.5 percent RPM. The governor works on the principle of spring force opposing engine speed (as sensed by flyweights). As engine speed increases, the flyweights move outward and push a rod. This rod is attached to the governor spring. As the governor spring is compressed, the rod contacts the servo bleed in the end of the metering piston. This causes the fuel flow to decrease, controlling the engine overspeed.\"

Interesting that they say fuel topping doesn\'t start until 104.5-105.5

So as primary RPM control you have the prop but should that fail then the fuel control can interact and \"try\" to limit the overspeed. This is referred to as \"fuel topping\"

Dan

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Dan Wilson wrote:

If your talking about the fuel control fuel topping (103%) it is far from a myth.

From the Lockheed Engine training manual (-7, B model book)

\"A flyweight governor, in the fuel control, limits engine speed to 104.5 to 105.5 percent RPM. The governor works on the principle of spring force opposing engine speed (as sensed by flyweights). As engine speed increases, the flyweights move outward and push a rod. This rod is attached to the governor spring. As the governor spring is compressed, the rod contacts the servo bleed in the end of the metering piston. This causes the fuel flow to decrease, controlling the engine overspeed.\"

Interesting that they say fuel topping doesn\'t start until 104.5-105.5

So as primary RPM control you have the prop but should that fail then the fuel control can interact and \"try\" to limit the overspeed. This is referred to as \"fuel topping\"

Dan

Dan,

The reason that the fuel topping governor is set between 104.5 and 105.5 is to insure that the pitchlock regulator has dumped it\'s fluid and the prop is pitchlocked. if you have a malfunction to the point that the fuel control is controlling the rpm via the Fuel Topping governor the last thing you want to do it have the propeller come out of pitchlock and try to control rpm.

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If it was the maintenance people, or fellow FE\'s I would maybe think they were talking about the fuel topping governor and doing the fuel topping test during an engine run.

Its been too many years for me, you have sprung lose a memory in my old mind. However the term \"Fuel Limiting\" comes to mind.

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I got CRS also.

When a plane would come in from a mission we would have the flt. crew taxi and park at the fuel pits.

We would refuel the internal tanks there unless there was maint. to be done like a PE. or fuel tank maint.

This is to the best of my knowledge.

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Bob Woods wrote:

If it was the maintenance people, or fellow FE\'s I would maybe think they were talking about the fuel topping governor and doing the fuel topping test during an engine run.

Its been too many years for me, you have sprung lose a memory in my old mind. However the term \"Fuel Limiting\" comes to mind.

Are you talking about the three stages of the TD system? Start Limiting, Temp Limiting and Temp Controlling?

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I\'m not sure what I\'m talking about, I remember doing pitch lock checks and looking for a certain rpm (104 ?), but I the only fuel topping I remember is the over the wing refueling to top off the tanks. Its been many years since I worked on hercs, since 73. I\'m amazed what I do remember, like all the bold face stuff is still in my head. Although I can\'t remember if its flaps or gear first.

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Different languages, different meaning, same words. US Navy guys talk about the \'fuel topping governor\', while the rest talk about \'fuel control governor\'. In South Africa and the UK we talk about \'topping up\' the tanks, while Americans talk about \'topping off\'.

BTW fuel governor rpm for -A15/D22A 103.6% to 106.1%, and -7/D22 is 103.6 to 105.8%

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You are correct about the different languages between the different military services, different countries.

Then you throw in the fact that some of the US Navy Pilots and FE\'s came from or went to the P-3\'s. Now talk about two totally different designed and thought process aircraft. Even though the engines were basically the same, and I have been to Field Maintenance school at the Allison (Detroit Diesel or RR) Factory in Indianapolis for the -10W/-14 engines and have been back to Intermediate Maintenance school for the -15/-16 engines, same parts or components are called anywhere from 2 to 4 different names.

And fuel governing for the A-10W is 103.8% to 106.0% and the A-14 is 103.9% to 106.4%. Bottom line is that the main purpose for the fuel control to start control engine RPM in those ranges are to ensure the Propeller Pitchlock Regulator has ported the propeller controlling fluid (by 103.5%) to pitchlock the propeller.

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pjvr99 wrote:

..... bearing in mind when the prop does over-speed, the fuel conrol governor rpm is set according to fuel flow, which mostly is around 104.5% to 105.5%

In my 25+ years of maintaining and being an FE on aircraft equipped with the T56 engine I have mainly seen the RPM ranges 104.5% to 105.5%.

In fact the P-3A/B Natops(Navy -1 manual) has a caution note in the Fuel Governor Pitchlock test that if the RPM is between 105.5% and 106.0% to investigate that the propeller is not governing the RPM.

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Okay guys, thanks for the answers.

What had me screwed up was I thought that 103.5 is what we always taught for fuel topping, but then I read that Lockheed manual the other day that said 104.5 to 105.5! Unfortunately I don\'t have any other references left to check it against and my pharmaceutical soaked brain just couldn\'t get out of the vapor lock it got into.

I really wish I would have kept my books, but after I was med disqualified I got rid of a lot of stuff; it was pretty painful for the first year, still in the Air Force and in a flying squadron but cant fly anymore:( (they just didn\'t want to go for that 15th waiver) At least I finally got past that point so now when I see one of you guys buzzing the house I can say \"you lucky bastards\" and not hurt too bad!

Dan

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Dan Wilson wrote:

Okay guys, thanks for the answers.

What had me screwed up was I thought that 103.5 is what we always taught for fuel topping, but then I read that Lockheed manual the other day that said 104.5 to 105.5! Unfortunately I don\'t have any other references left to check it against and my pharmaceutical soaked brain just couldn\'t get out of the vapor lock it got into.

I really wish I would have kept my books, but after I was med disqualified I got rid of a lot of stuff; it was pretty painful for the first year, still in the Air Force and in a flying squadron but cant fly anymore:( (they just didn\'t want to go for that 15th waiver) At least I finally got past that point so now when I see one of you guys buzzing the house I can say \"you lucky bastards\" and not hurt too bad!

Dan

Dan,

Everytime we have moved, my wife has bitched me out for all the \"books\" I have kept. It wasn\'t until after I retired and we started really mingling with old squadron mates that she figured out some of the things we did. I have been a FE on P-3A/B/C, C-130A/E/G/H/T, B727-100/200, L1011-50/100/250/500, L-188, KC-97G, C-118, DC-8 and have the flight manuals (at the least) for each of them. For the L1011 I have over 70 pounds of manuals and charts...I know that because I shipped them al at one point to someone I was consulting with about operating a couple L10\'s

I feel for you for being DQ\'ed for flying. The only thing I think that was worst was the Navy...being a FE was a collateral duty and you had to perform your primary MOS/NEC also. I was a Aviation Metalsmith (airframe/flight control/LG/HYD...etc.) so I ran the airframe shop, when I got to be an E-6 started working QA, and Maintenance Control and flying 40 to 100 a month also. Got passed over numerous times for E-7 since I would not give up flying...in the whole Navy during the 80\'s and 90\'s there was only openings for 14 E-7 C-130 FE\'s, 4 E-8 and 2 E-9\'s. So it was tought to be promoted to E-7, E-8 or E-9 and knowing you would be grounded...and it was a good chance in the great Navy wisdom to transfer you to a fighter or helo squadron where all your system knowledge would go to waste.

Don\'t feel bad Dan, you have forgotten more then a lot of us ever knew.

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Dan Wilson wrote:

Okay guys, thanks for the answers.

What had me screwed up was I thought that 103.5 is what we always taught for fuel topping, but then I read that Lockheed manual the other day that said 104.5 to 105.5! Unfortunately I don\'t have any other references left to check it against and my pharmaceutical soaked brain just couldn\'t get out of the vapor lock it got into.

I really wish I would have kept my books, but after I was med disqualified I got rid of a lot of stuff; it was pretty painful for the first year, still in the Air Force and in a flying squadron but cant fly anymore:( (they just didn\'t want to go for that 15th waiver) At least I finally got past that point so now when I see one of you guys buzzing the house I can say \"you lucky bastards\" and not hurt too bad!

Dan

Dan, does “the fuel control starts to reduce the fuel to the engine at approximately 103.5 percent rpm†sound familiar?

So the 103.5 was never a hard number, at least as far back as I can remember.

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Okay, thanks guys - I think I have all the numbers back where they should be :)

At least the guys still working will have more use for the Lockheed manuals and Alison books than I will. What the heck, I still have my \"Herky Handbook\" and the -7 engine/prop Lockheed book that got missed in my housecleaning:cheer:

Dan

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The only fuel topping that i know is during the pitchlock check of the Prop during an EGR after a prop change. Make sure that the RPM guage hits 104% (indicated) during the check to make sure the FCU has taken over the governing. In the field you cannot check evereything to Lockheed specs but you can make sure the engine is working. As to the prop oil check, the Canadian system of checking prop oils every 28 days with two guys is very workable. This system has been adopted by the Brits and has reduced our low prop incidents to a manageable level. The only time whe get prop low oil level lights is due to a malfunctioning low level float valve. In 15 years of flight line ops we never had a problem with incorrect prop oil due to incorredt servicing.

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