Thorp Air Command - T18.net

Many of the round engines have an electrical driven pre oiler. A/S has one in there catalog.
Phil
118BC

I was only referencing my experience with engines so you know where I am coming from. Lycomings are definitely a different beast than what I have serviced.

I agree on the air being a huge portion of contaminate in the engine. Proper filtration on the intake air is key to a clean engine.

As for the pre-oiler we use a pressurized accumulator that stores a slight amount of oil pressure in it. Close off the valve before shut down then before start up open the valve and the stored pressure moves oil through the engine. I don't think this would add much weight to the system. Possibly less than an electric motor. Cranking without spark would be a poor mans pre-oiler and work well (battery depending).

Getting back to weight and balance, I am wondering what is the weight of tail that other A/C have. My tail weighted about 38 Lb's. with the A/C level. This is with a O360 and a constant speed prop. I am finishing a lot of work on the A/C including a new interior and need to reweight the A/C to get a accurate W&B. I have been advised that around 45 Lb's is normal???.
Phil
118BC

Other W&B sheets I have been able to find online and the "example" in my paperwork are all below 50 pounds. I am concerned that mine shows 67 pounds. If I can get some help getting the scales down and can find containers to store fuel, I am going to try to weigh mine today. I may just have to go burn some fuel while boring holes in the sky...what a depressing concept

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

Jeff, who's plane did you buy again? I may have an idea as to why the W&B is strange.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Ok Jeff, So that's Chuck S old airplane. I'm thinking you're looking at a math issue. That plane had a Ford V6 on the nose before, he put Les Conwell's 0-320 on it right before it was sold. The V6 is significantly heavier than the 0-320. I'm thinking perhaps he put weight in the tail to counteract the V6 and then added weight in the nose to counteract the loss in weight. The V6 is about ~100lbs heavier than an 0-320 so there must have been a W&B effort related to the retrofit. Perhaps he shifted the weight in the wrong direction by accident ... either way you need to put it on scales again.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

You are right, it needs to go across the scales. When the aircraft was first built it had an O-290 with a 74DM prop and the tail weighed 57 pounds. When the V-6 went on the tail weighed 44 pounds and now with the O-320 installed the paperwork shows 67 pounds. There are no equipment lists or revised W&B sheets to let a person know what was accomplished and/or included on the aircraft when it was weighed. It looks like anytime he changed something major he weighed it (at least 4 times since 1974). Only the first and last W&B are actually dated. No mention of the lead anywhere in any of the aircraft documentation.

If Chuck's numbers are correct (the math looks pretty good), the aircraft would be at the aft CG limit without the lead on the engine if you figure 340 pounds in people and minimum fuel. Remove the fuel and it breaks the aft limit by a quarter of an inch. I am not willing to try it until I weigh it and crunch the numbers myself since flying tail heavy airplanes can drastically reduce one's lifespan. Probably can't fit 340 pounds worth of people in and manage enough movement to fly the thing anyway.

Using the existing W&B info, the aircraft weight difference between the V-6 and the O-320 looks to be about 190 pounds. It will be a bit of a project but I intend to remove the radiator mount the first chance I get. I am guessing it weighs 5-10 pounds and is located about halfway down the tail. There is no ballast in the tail.

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

Let's just say I'm pretty sure I saw more than 340 lbs (two people) in a T18 fly perfectly well at KY Dam with substantial fuel on board to boot. They both said it was "cozy" but done with apparent ease.

I refuse to name the individuals involved.

340 lbs? That's only a couple of "average" 170 "pounders"... not even close to what a normal Thorp can handle. I'm skinny, and I weigh 180.
I think you're probably being a little facetious, but I have had over 450 lbs. of people in my T-18. Very little in the baggage compartment, but full fuel. It flew just fine. My 6'5", 270 lb. passenger had to take his cowboy boots off though - the guy had long legs. I'm used to flying the Thorp with basically just wrist movement of my left hand. Shoulder room is the usual issue. If fat legs are going to impede stick movement, I just take the stick out.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

John,
I hope you mean on the passenger side.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

Some of you guys have heard this before. I loaded my S18 with two Model A Ford blocks, two crankshafts, 25 pound tool bag, case of beer, duffle bag with clothes for two weeks, bag of pepperoni rolls, I think there were a few brownies, can't remember as I ate them and 62 gallons of fuel. Did have the stick removed on passenger side, and flew out of CKB back to Florida non stop to LAL. I estimated gross was just under 2000. The RV guys could not believe I could get that much into the Thorp as they helped unloading it.
I would not recommend this and have not done it again. N30WW 180 Lyc constant speed.

If operated as a Normal Category Aircraft, the T-18 can go up to 1973# Gross Weight. Don Taylor's around the world Thorp had a max T/O weight of 2200#. Just to start a conversation, fuel in the wings doesn't count for gross weight calcs in-flight because it is self supporting.

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Bob Highley
N711SH
SN 835
KLAL

I really didn't expect an off-handed joke about how small the the T-18 is to garner so much attention. It is impressive you were able to pack that much cargo into the bird. The power to weight ratio on your bird is still pretty impressive at 2000 lbs.

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

I would think it would have to count for gross weight. The fuel itself doesn't not support any weight but the structure must support the fuel. It may be better distributed but it is still a load on the wing and the heavier the load the less maneuverable the aircraft is in flight. Do you have a source for someone to research further?

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

I think you are correct there Jeff. It does add to the gross weight. If it didn't then I wouldn't have to calculate fuel on my piper cherokee for gross weight since it is a wet wing.

The wing fuel is a better distribution so it won't upset the CG as much but it does add to gross weight. I'd like to have wet wings so I don't have as much CG change in flight with this forward tank. It's just not feesable to keep changing things on my plane at this stage though.