Long range capabilities of 337 and modifications

[stratobee]

As I understand it the bog standard early 337 models came with a 128 gallon tank. The later factory long range ones had a 148 gallon from what I can understand.

Aviation Enterprises website says they can fit up to 408 gallons into a 337 and I was wondering where all that would go! Some it seems goes into under wing pods. Anyway, it piqued my interest and I now need to turn to the expertise on this forum for answers.

Can someone explain to me what the modification options are within the wing? What's the capacity one can fit in there at the most? And is it better to go with a wingtip extension combination or something else?

Also, are there baggage compartment aux tanks available like you can get for the single Cessnas? I haven't found any such online, but maybe there's a source I haven't found?

I'm researching the feasibility of getting 1700nm range out of it, which would help her get directly from Shannon to St. Johns or to do the southern Azores transatlantic crossings in the winters. I've calculated that at optimum range (125kts) it would burn about 14 gallons/hr, which would make the total needed around 190 gallons on the Shannon-St-Johns route, with no winds. You want at least 2-3hrs on top of that, which brings you to 220-230 gallons. Now, would that fit into the wings with modifications?

[Skymaster337B]

Realistically I'd plan for 18 gals/hr...but more like 20 to play it safe.

[Ernie Martin]

I wouldn't quarrel with the 14 gal/hr at the reduced 125 kt speed and assuming lean-of-peak operation (which requires matched injectors such as GAMI, cylinder-by-cylinder engine monitoring and a knowledgeable pilot). And "stratobee" has put the margin in the additional 2 - 3 hrs that he's budgeting.

I wouldn't do it myself, but the numbers look OK.

Ernie

[stratobee]

I'd like to ad that I wouldn't fly that route myself, I'd have it ferried by a more experienced pilot. It's just that if it does that trip more than twice, then the mods probably make sense compared to the hassle of a ferry tank. Obviously there's always the northern route that needs no mods at all, but at winter that can be hazardous.

[Roger]

Holy crap. What a waste of money and effort.

[WebMaster]

Your best shot is internal, inside the cabin, Ferry Tanks.
These are custom made, will require some plumbing and pumps, to get the fuel to your wing tanks.
Owen adds internal to the wing tanks outboard of the current tanks. These are small tanks, several of them, in each wing. With each tank there is a fill port, and a fuel drain, both of which add to the drag on the airframe. Then there are the wing extension tanks. These are ever further outboard of the wing end. Finally, there are the under the wing tanks, attached with hard points under the wing. All of these tanks require additional plumbing, and pumps to work.

The deal about all of those is that they are expensive, they are modifications to the airframe, that place additional loads on the wing, in an area that is not necessarily designed to take those loads. In addition, when you are all done, they are there forever.

If you get an internal ferry tank, you can take it out when you reach your destination. You can take off at 30% over gross weight, and not affect the drag that is on the airframe.

I remember listening to someone talk at the last Bahamas fly-in about flying from St. Johns to the Azores. It was the shortest route to go to Africa. There was a temporary installation of a HF radio, mounting it up in the cabin overhead. The route is direct, over well traveled shipping lanes, and avoided all the potential for icing that can be found on the northern route.

In the fuselage tanks were used by the AF to ferry 0-2's to Viet Nam.
I would suggest talking to Don Nieser about installing a fuselage tank. I think for long distance, this is your best bet.

[hharney]

Visited a booth at Sun N Fun but can't remember the name of the company. I will keep looking but here is one that I found.

http://www.turtlepac.com/products/bu...l-bladder.html

[stratobee]

Thanks for the info.

A ferry tank is both cheaper and easier when you ferry to Europe. However, if the aircraft ever has to go back, it needs a whole slew of approvals from various dignitaries and national air authorities. This is Europe after all. Last I heard a ferry tank would need a £6000 approval or temporary type certificate from the UK's CAA... That's why the built in option is desirable - they can't mess with that if it has a US STC.

The nature of my job is that I might spend 6 months in the US, then 6 months in Europe. That's an awful long time to be away from an aircraft you own. And owning two aircrafts, two insurances? I'm afraid I'm not that rich.

But who said aircraft ownership should be easy?

[rhurt]

Another option is to put a tank in a cargo pod. The pod would proably cost about 2 mph at 125kt.

[Dave Underwood]

My two pennies worth are as follows:

1) You have 128 gals in the aircraft which at 145 kts and 20 gals/hr gives you 6.4 hr range or a safe range of circa 600 nm, ultimate range being just over 900 nm.

2) Take either the the far north route and you have more than enough range on each leg, or take the southerly route via BGBW (Narsarsuaq) east bound with tail winds and your longest leg is 670 nm.

3) You may well want to take the northern route west bound with the head winds and lower ground speed, with the leg lengths circa 400 nm. Great scenery as well either route.

4) You just can't really do either crossing from November through March though there are lots who do. Icing and very poor weather and serious head winds.

5) On the southerly route via BGBW, unless you can fly at 25 k, you will need an HF radio.

6) The above options do not require any aircraft mods, though if you could get the extra 20 gals, you increase your safety margins and comfort factors.

7) There a several folks around who will put a tank of reasonable size in the back and plumb it into the fuel return lines. You then face all the paperwork challenges every time you want to do a crossing and have the tank refitted.

8) A better thought might be to put in a smaller tank on a Form 337 and leave it in place for Northern routes. That would be my choice.

9) The 30% extra fuel requirement on any crossing means on the St. John to Portual route you would need about an extra 150 to 170 gals or close to 300 gals. You may have to do work to strengthen the floor to carry the extra loads.

10) I think if you talk to any of the ferry pilots who do the trip regularily, the answer would be to make it simple and go one of the northern routes.

D

[stratobee]

Thanks for your responses.

[Cole5Oh5]

What kind of Skymaster do you own?
If none, then I would recommend a P Model to get above the weather you would encounter on the northern route.
It will save you a lot of grief, instead of adding tanks.

[stratobee]

I don't own one yet.

Love to have a P model, but for my budget it's going to be one of the early normally aspirated ones, I thinks.

[skymstr02]

Originally Posted by stratobee

I don't own one yet.

Love to have a P model, but for my budget it's going to be one of the early normally aspirated ones, I thinks.

There's nothing wrong with a normally aspirated 337 airplane