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  #1  
Old 03-04-16, 09:24 PM
YankeeClipper YankeeClipper is offline
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Is it possible to de-rate a pressurized aircraft?

I've read plenty about the benefits and costs of pressurized cabins. I'd love to cruise 10k with nary the pop of an ear (truly--I have terrible issues with my ears and pressure changes), but the costs of a P-model are just beyond the budget for my mission. But if I could take the quiet and weather resistance of the P, and lose the maintenance and insurance costs, it would seem ideal. Nice thing is, it is not unreversible, unlike, for example, welding up gear for similar objectives.
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Old 03-14-16, 11:12 AM
YankeeClipper YankeeClipper is offline
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To clarify, I'm wondering if it is possible to remove--for lack of a better word--the pressurized rating of the aircraft, so as to remove the constraints and obligations associated with that (insurance, oxygen, etc). Naturally, I would also be flying it as a non-pressurized aircraft at that point.
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Old 05-05-16, 05:59 PM
klpilot klpilot is offline
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Quote:
Originally Posted by YankeeClipper View Post
Naturally, I would also be flying it as a non-pressurized aircraft at that point.
Why not save the hassle and buy a non-pressurized airplane in the first place then?
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  #4  
Old 05-13-16, 06:11 PM
YankeeClipper YankeeClipper is offline
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As I mentioned in the original post, the pressurized hull has several perks over the non (along with some disadvantages too, of course).
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Old 08-08-18, 04:32 PM
YankeeClipper YankeeClipper is offline
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Wanted to post a follow up for posterity.

According to a local IA, you cannot de-rate, however, you don't have to fly with the pressurization working. In other words, you can decline to fix issues with the pressurization system, as long as the IA believes it doesn't pose a threat to safety or proper operation (beyond pressurization itself).

Alas, those issues are, according the same source, but a fraction of the costs associated with 'P' models. The obstruction of the additional systems accounts for much of the additional costs. The extra boost of the 225 turbo, unless faithfully reigned in by a determined pilot, burns up components a little more quickly than the 210 turbos, and much faster than the NAs. This, not from my own experience.
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  #6  
Old 08-09-18, 10:34 AM
rrolland rrolland is offline
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Your IA is correct. You can choose to opt to fly with the pressurization inop. Just like you can choose to fly with it turned off (there is an on/off switch).

You cannot remove the system in however -which I think you mean as de-rating- as the pressurization system is linked and a part of other systems such as heating (combustion heater) and ventilation. By opting to fly with the pressurization inop, you end up carrying the weight of the system for no benefit.


As mentioned somewhere else though, the pressurization system has proven reliable for me. As have the turbos.
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  #7  
Old 08-09-18, 06:39 PM
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hharney hharney is offline
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The pressurization system on the P model is probably the simplest systems in the aircraft. Other than leaks in the pressure vessel, there is really nothing else that is a concern. It works well but is only a 10,000 ft cabin at 20,000 ft. When comparing pressurized planes that's not much differential. There is a purpose for the P model so don't make it what it isn't. The added weight to the P model is substantial so why would you buy one and then not have a use for the very purpose of the model? I could never understand when folks wanted to make the 337 a fixed gear airplane. But I am sure someone could come up with a reasonable reason.

What's the mission, as you have described in other threads, buy the model that fits the mission. One thing to consider is the environmental system (cabin heat) for the Turbo and the P model is a Janitrol gas heater. With the normal aspirated models the heat is directly off the mufflers. The Janitrol can be a finicky item and expensive. Maybe you are familiar with them, have you had a gas heated aircraft? I have always thought simple is better but in some cases the mission requires the gas heater.

With your mission being 1-3 hours twice a month in the North East it may be that a normal aspirated Skymaster will do a really good job for you. These flights may be easily accomplished with the standard NA airplane. If weather dictates ICE there is NO Skymaster model that can launch into Known Ice. So if weather keeps you from going and you have to be there then you are looking at the wrong airplane. If you can say leave a day earlier or stay a day later for the weather to pass then the Skymaster will do the job. Even the P model at Flt Lvl 160 or 180 won't get you over most summer weather. It may provide a better ride but you will still be deviating for build ups. You didn't mention how many seats are required. If most flights are 1 -2 people then a heavy plane with work but if you need 4 seats for adults then the P model can be restrictive. Fuel loads for 1-3 hours are pretty simple in any of the models. The occasional long trip every year will require a fuel stop but once a year is reasonable. If you can afford the P model price and upkeep then it's a great tool for what it does but there are a lot of Skymasters sitting because someone bought them and can't keep them in the air. Fuel cost and maintenance grounds them because the low purchase price attracts a buyer that can't maintain the airplane. Therefore it makes for a difficult quest to find a good, well maintained Skymaster aircraft. The good ones just aren't listed for sale because the market won't justify selling the aircraft for the money they are worth. Owners keep them because they love them and can't really justify something else.

Bottom line, find a 337 that has been taken care of, that fits your mission or be prepared to spend some money to bring the airplane up to standards. The best Skymaster to buy won't be listed on all the usual sites. It is being flown regularly, maintained and you will have to sweet talk the owner in selling the plane.
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