Fuel systems - Page 2

kevin · #16 10-07-03, 09:43 AM

Depending on what year/model you have, how it is equipped, how much your passengers weigh, and how much luggage they have, you may or may not be able to put four people and full tanks in a Skymaster and stay below gross weight. Fore example the max gross on the '65 is 4400 lbs as I recall, as much three hundred pounds less than later years.

I would encourage all Skymaster pilots to do a weight and balance calculation for *their* airplane before taking the advice in this thread.

Kevin

Ernie Martin · #17 10-07-03, 10:45 AM

I agree with Kevin: there are times when you can't fill the tanks without exceeding gross weight limits. I have carried as many as 6 people to a Bahamian island 160 miles away. No fuel on the island. Do the math. With some luggage, six people can weigh 1100 lbs, and it's clear that full fuel (750 lbs) will exceed my 1664 lbs limit. Since the trip typically uses 50 gal, I can have a sizeable margin and still meet weight limits by loading 80 gal, instead of 125.

Most of you know my concerns about fuel starvation and fuel mismanagement, and the steps I've taken to help others avoid them. Full tanks is nice but you can't do it all the time. At some time in your life there will probably come a trip when you can't load full fuel. And it is precisely in those instances when you most need to understand your system and its operation.

Ernie

Dale Campbell · #18 10-07-03, 01:38 PM

Most of the time I fly with just pilot and co-pilot. So I keep the tanks full or above 80 gallon. If I plan a trip with four on board I know I have to keep fuel under 80 gallon. So thats how I plan it.
In winter to keep out condinsation they are better to be full. But as you said you must always check your gross if you fly with more than 3 people or if you take baggage. I have not had my two back seats in even once since I bought 337H 3 years ago. Never had 6 people on board.

Damon Banks · #19 10-08-03, 02:37 AM

It's not just the Max Take-Off Weight you have to watch either.

I find that the Max Landing Weight - 4465 lbs in our 74 P337 is the limiting factor on short trips (MTOW 4700 lbs).

I reckon there's a good market for an STC to be developped in this area - increasing the MLW to be the same as the MTOW - any takers out there?!

By the way, does anyone know what the limiting factor on the Max Landing Weight is? ie - what has to be modified to increase it?

Damon

Mitch Taylor · #20 10-08-03, 12:28 PM

I think to increase max landing weight, you'd probably have to rebuild the whole airframe. Landing gear, wing attach, spar strength, all have to do with it. The g stress you put on the airframe when you touch down a little hard is way different from the stress from taking off.

Paul Sharp · #21 10-15-03, 05:03 PM

Noticed a couple of queries on the first page of this thread asking about my model (sorry, but didn't see them earlier). I have a 1967 Turbo B model.

It has separate tanks, separate fillers, separate caps, and fuel selector positions for main, aux, cross-feed, and off.

Here's a little more thinking. I checked my BEW yesterday (hadn't looked at it in a while), and it's 1377. So if I put full fuel in (128 gals. = 768)), I have a usable weight of 609 bls. left. That means I can take 3.48 FAA (175 lbs. each) passengers, but in reality I always get the weight of the people involved and go by that. If there is baggage then there's more to figure and deal with.

I usually leave my main tanks full and the aux. at 7 lbs. each. That's 624 lbs. of fuel and means I have a remaining useful load of 753 lbs. - which is four FAA passengers and 50+ lbs. of luggage. So I seldom even worry about the weight but just keep the heaviest up front during loading (empty CG is always nearer the reat than front on mine). If I know I'll start approaching the limits then I start planning on how to deal with it. Once we had 5 people in the plane, but 2 were well under the FAA's 175 lbs., and there was very little luggage for the 2.5 hr. trip. So I didn't even have to leave fuel out from the previous trip.

I definitely agree that you need to be sure to know the weights involved, and any time there is a question you have to get out the scale and figure things out, being careful to track the loading for CG too.

I like the 7 lbs. in each aux. even if I need to reduce what's in the mains because if you throttle back you can easily get 1/2 hr. of flying from them and if you really got stupid you know you can switch to the aux. tanks and start looking for a landing place pronto. If you don't have anything in the aux. tanks and got stupid you may not realize it until an engine stops and then you're out of options.