Fuel consumption/Relief tubes and related

I am considering buying a 337G and am trying to get a feel for its range. I do not have access to the Pilot's Operating Handbook. What would be the approximate fuel consumption in gph and TAS at 65% and 75% power at say 15,000 feet?

[SkyKing]

First off, the mission capabilities of a normally aspirated 337G would be most difficult at 15,000', as these units are not equipped with oxygen and they are normally aspirated.

Even with the dual centerline thrust TCM IO-360's, the airplane's Service Ceiling is 18,000' with both mills turning. Front engine only is 6,900' and with the rear only, 7,100'.

Cruise configurations for the 337G (1977 model year) using recommended lean mixture with fuel allowance for engine start, taxi, takeoff, climb, 45-minutes reserve at 45% and descent will net the following:

75% power @ 5,500' with 528 pounds of fuel: 545nm/3.3hrs

75% power @ 5,500' with 888 pounds of fuel: 990nm/5.9hrs

MAX Range at 10,000' with 538 pounds of fuel: 670nm/5hrs

MAX Range at 10,000' with 888 pounds of fuel: 1,235nm/9.3hrs

Takeoff at full gross: 1,000'; over 50' obstacle: 1,675'
Landing ground roll: 700'; over 50' obstacle: 1,650'

Stall speed: (CAS)
Flaps up, power off: 70 knots
Flaps down, power off: 61 knots

Rate of climb @ sea-level: 1,100 FPM

MAX WT:
Takeoff - 4,630 lb
Landing - 4,400 lb

Standard Empty WT: 2,790 lb; Skymaster II: 2,913 lb

SkyKing

[SkyKing]

Whoops... forgot the speeds:

Maximum at Sea-Level: 179 Knots
75% Cruise power @ 5,500: 169 Knots.

Now, if you adopt a P337, at 16,000' with 2400 RPM and 31" MP (67% Power), your cruise speed would be 191 Knots with a total fuel burn of 144 PPH (24 GPH).

I don't have the figures for the non-pressuried but turbocharged 337H (T337H) which was only manufactured in 1978, 1979 and 1980, but one of the members of this board, Don Campbell, has one and perhaps he can provide some figures.

Keep in mind the T337H has 210 HP engines and smaller blowers, whereas the P337 (or T337G) has 225 HP engines.

SkyKing

Skyking in right re: non-pressurized ac.

I've got a 337A normally aspirated, and it takes a LONG time to get to 15,000, and . . . of course, requires supplemental oxygen. However, sometimes, the winds are good enough up there on a long trip that patience and supp o2 is rewarded.

If you buy that or any other non-pressurized bird, my unsolicited opinion is that it's worth your money to buy supp o2 regardless because it just makes life easier, safer, and more flexible. Plus, anytime I go over 7000' on a long trip I use it towards the end of my flight just to knock the edge off and eliminate any "hangover" effect.

It's worth the $.

Keven
________
Suzuki Dr650 History

Thanks to all for your good advice. I have now determined that the airplane I'm going to see is a 1973 P337 with Continental TSIO360CB engines. I was trying to determine the range for this specific plane, and it looks like I will be able to make a safe 800nm flight if my rear end can hold out. If I can make a TAS of 190 kts at 16,000' with a fuel flow of 24 gph and a fuel capacity of 123 gallons, I can

[SkyKing]

Dear "cbrsrceo"...

Here are the numbers for a 1977 P337 with 148 gal fuel:

Max speed @ FL200: 217 Knots
Cruise, 75% power at FL200: 205 Knots
Cruise, 75% power at 10,000 feet: 186 Knots

Max Range at FL200 with 888 pounds usable fuel: 1,155nm/7hrs
Max Range at 10,000 feet, ditto on fuel: 1,110nm/7.3hrs

Nominal Range @ 75% power at FL200: 985nm/5hrs

The nice thing with turbos, rate of climb is still 870 FPM at FL200 at full gross, and you'll always be climbing faster that the 337G counterpart.

Best of all, at FL200, your cabin altitude will be around 10,000. If everything is in proper operating order, the P337 should maintain a sea-level cabin up to 7,000 feet, and in between at say 14,000 feet your cabin will be down at 5,500 feet. There is also a distinctive quieting effect of pressurization.

The above figures are from the POH.

BTW, you'll want to be aware that most of the early P337's, say 1973 vintage, still had (or have) the TSIO-360C engines and a number of those had a potential problem of cracked cases, mainly on the rear engine position. The CB6 version seemed to cure that TCM 'defect'. Of course, this won't be a problem unless the plane has the original engines SNEW.

SkyKing

[kevin]

Just for another viewpoint, I own and regularly fly a 1973 P337 with 123 gallon tanks. Your calculations seem to have forgotton wind, reserve for taxi, runup and climb, potentially unusable fuel, and reserves. I flightplan 10 gals for climb to 16,000, and 25 gph for cruise. This is a bit too much, but seems to work out within a few gallons. Therefore, the fuel exhaustion time for my airplane is approximately 4 hours and 45 minutes from takeoff. I run at 65% power approximately 65 degrees rich of peak on the first cylinder to peak. I will in fact get a TAS of 190 kts at 16,000, but headwinds more often than not reduce this, such that I use 170 kts as a flight plan groundspeed. I try to land with 60 minutes of fuel left, therefore my max range is 3:45 at 170 kts, or in other words, 637 nm.

With no reserve fuel at all, I calculate the range for my airplane to be 807 miles, assuming a 170 kt groundspeed.

You might barely be able to make such a trip at a very low power setting, perhaps 45% power. You'd still have a 140 kt groundspeed in that 20 kt headwind, and you'd land with a bit over 30 minutes fuel. I can't vouch for this, I have never run the airplane at such a power setting.

If you need 800nm range, buy a later model Skymaster - a H model, with the 148 gallon tanks. I wish I had them.

Kevin

[SkyKing]

Kevin, et al...

The 'Big Tanks' for the Pressurized Skymasters came along in the 1975 model year. That's when Cessna went to 4-tanks per wing, bringing the total usable to 148 gallons. Standard tanks for the 1973 and 1974 models were 92 gallons usable, with a long-range option totaling 118 gallons and these model years had 3-tanks per wing. Not sure when the fuel was increased to 123 usable, as in your case.

BTW, a later year "G" model of the pressurized series will also provide 148 gallons usable. Type certificate "T337G" is a P337 for those unaware.

Serial number & model years for the P-models break down as follows:

1973 T337G: P3370001 through P3370148
1974 T337G: P3370149 through P3370193
1975 T337G: P3370194 through P3370225
1976 T337G: P3370226 through P3370257
1977 T337G: P3370258 through P3370292
1978 T337H: P3370293 through P3370318
1979 T337H: P3370319 through P3370341
1980 T337H: P3370342 through P3370356

All of the above are Pressurized Models.

SkyKing

[kevin]

Skyking,

Thanks for the info about later G models having the large tanks, I didn't know that.

As for 118 gallons, I have heard this number before, and I am curious where you got it. I am looking at the owners manual for my airplane - a manual for the for correct year and model (1973 T337GP). On the inside front cover, under total fuel capacity, it says 125 gallons. On page 2-1, first paragraph, it says "The fuel system is composed of three interconnected fuel tanks (369 pounds total usable fuel) in each wing and one sump tank in the lower portion of each boom." 369 x 2 = 738 / 6 = 123 gallons.

If it only has 118, I'd like to know that. If you have time, I'd really appreciate knowing where your number comes from...

Thanks,

Kevin

[Jim Rainer]

Kevin,

I don't know about the "P" models but I think the 118 gallon number is usable fuel in the normally aspirated models with the small tanks - but this should be in your FM!

[stackj]

Fuel range - approx 6 hours
Bladder Range - Just over 3 hours

Safety Factor - just under 100%

[SkyKing]

For those of you with later P-models with the Cessna 'advertised' long-range tanks (1975 and later - the 4-tank arrangement)... if you have a Roberston STOL kit installed, the outboard tanks have been replaced with a slightly smaller tank to accomodate the Robertson rigging mechanism that allows the ailerons to be lowered with the flaps... your usable fuel is 71.5 gallons per side, or a total of 143... not 148. You might want to check the overhead fuel selector switches and make sure they're correctly placarded.

And Kevin... that 118 gallon figure was just stuck in my memory bank, but since you have the 1973 POH, you're information is more probably correct. When I was searching the marketplace, I happened on to 1973 with R/STOL and for some reason I recall the owner telling me his usable was 118 gallons... that's where the figure came from. But since the earlier P-models only have three tanks, I wouldn't think there'd be any penalty of fuel since there's nothing out there in the wing ends to interfere with the R/STOL rigging.

In any event, it's nice to have 148, ahhh, I mean '143' gallons usable with our R/STOL equipped bird, but like it's been said, the bladder capacity keeps the range much shorter!

Besides range, one additional benefit of the long range tanks is to be able to 'tanker home' some cheap fuel... WHEN you can find a deal. I recall when we had our FBO in the 70's, we were selling 100/130 and 100LL for $0.62 a gallon... and lately we're having to fork out $2.30 a gallon... are we getting screwed now, or what? Geesh... from $14.88/hour to $55.20/hour just for gas!! (based on 24/gph)

SkyKing

[WebMaster]

We recently went down to Indiana, after reviewing AirNav, had breakfast at RCO. On the way back, we stopped at OXI, and filled up the tanks on $1.75/gal fuel, and flew it back up to MI, where the discount is $2.68/Gal. We have the long range tanks in our 69 337D, and I was able to take on 102 Gallons, meaning I had 27 useable left, or more than an hour. It was worth the trip, and we had a pleasant breakfast.

[FRED-E]

Now you have me wondering, is my 1967 337B the only one with a pilot relief tub?
BTW if your ever through Oklahoma, just below Wichita, stop in our fuel is $ 1.85/gal (F22) Cushing, OK.
And oh yes, we are having our annual fly-in this week end, saturday, 9/7/02. Come one, come all !!!!!!!!!!!!
Fred N358

[kevin]

My old '65 C337 (N2223X) had a relief tube. Disadvantage to the P models, which is ironic...

Kevin

(Sorry.)