[captbilly]

I didn't see much info on the P model in the link so I though I would add some info specifically on the Pressurized skymaster. I owned one for about 5 years and overall I really enjoyed the plane, but there are some things you should know as well as some incorrect info floating around about the P model skymaster.

Performance: The factory claim of 205 knots at 20,000 ft. and 75% power seems right on to me. I generally ran closer to 65% but saw about 200k true. I have heard that the Riley intercooled models will cruise at close to 220 at 20,000ft. but I can not confirm this. Fuel burn for me always seemed to average 30GPH even though I was running 65% power and the fuel flow gauge showed closer to 20-25 GPH. The engines did not run hot in either climb or cruise and I virtually always cruised with the cowl flaps closed. The engine had a tendency to miss when cruising at 20,000. Some people claim that the missing is caused by some sort of vapor lock, but others think it is due to the unpressurized magnetos arcing. I know that many people have switched to pressurized mags but I do not know if this cured the problem. I am fairly sure that the certified ceiling limit of 20,000 feet was related to the mags because the turbo skymaster (which came with pressurized mags) does not have a 20,000 limit. In addition the P210, which uses an identical pressure differential of 3.2 psi, has a limit of FL230, so the cabin pressure would not seem to be the issue.

All P models are 5 seat aircraft due to having only a single door. FAA requirements specify a second emergency exit for more than 5 passengers, but the P 337 has only the main cabin door. In reality most P337 owners leave out the 5th seat because with it in place there is virtually no baggage space, and getting in and out of the 5th seat is quite difficult for a normal sized adult. I would call the 5th seat a reasonable place for a child on a short trip, but that's all.

IFR range of the 1973 models with 125 gallons is about 3 hours realistically. With an average fuel burn of 30 gph you end up with about 35 gallons reserve at the end of a 3 hour flight, so figure a realistic 600 mile range for the 1973 model and 750-800 miles for the later models with 150 gallons of fuel. For VFR range add 150- 200 miles if you fly at 65% and close to 20,000 ft.

Maintainence for a pressurised Skymaster is about the same as any other pressurized twin. The cost of engine overhauls has much more to do with number of cylinders than it does with the size of those cylinders. The TSIO360d in the P model skymaster has all of the same turbos, manifold pressure controls, fuel injection system and other accessories as any other turbo 6 cylinder, so overhauls will cost nearly the same as a TSIO 540. Obviously there are differences between models but a fuel system overhaul or turbo overhaul on a 360cuin engine is pretty much the same as on a 540cuin engine. A cylinder costs pretty much the same regardless of size, so any 6 cylinder will set you back about 50% more than a 4. The pressurization system, landing gear, wings, control surfaces, etc. of the skymaster, require the same attention and cost as any other pressurized plane, so figure on paying a similar amount to maintain a skymaster as you would a 340 or 414.

Many older Pressurized Skymasters have deteriorated quite badly due to defered maintainence. The problem was that for a while the P skymasters were so cheap that anyone could buy one, but not everyone could afford to properly maintain them. I bought a nice 10 year old P337 for $36,500 in 1983 (about the cost of a couple of good engine overhauls), and some were going for less than the cost of the engine cores. I had an anual inspection that cost me $20,000 (not typical but not insanely high either), so you can imagine what would happen to some P skymasters when the owner was faced with repairs that cost nearly as much as the plane. By the way that $20,000 annual included no engine work, just windows, and airframe stuff. The maintainence of P skymasters has improved as their cost has gone up, and as the cost of fuel has gone up. At $5 or more per gallon the cost to fly a P337 is $150-$200 per hour just for fuel so the rule of doubling the fuel cost to get the actual cost of ownership is much more realistic than it was when I was paying $1 per gallon ($0.50 in Mexico).

Fuel system: The P model has an extremely simple fuel system. From the pilots perspective there are just two tanks, left and right. There is only one filler for each set of tanks (left set right set) so you don't have to watch the line boy to make sure he fills the correct tanks. In flight you simply monitor the fuel level of the left and right tanks (all tanks on one side are measured together) and if you have set very different power settings on the front and rear engines you might have to crossfeed (I never had to crossfeed in all the years I had the plane). The fuel gauge is totally inadequate for anything other than telling you roughly how much fuel you have. It is a tiny little guage that will let you know within perhaps 10 gallons of what you actually have. I would really recommend a good fuel totalizer for some peace of mind when trying to press the range to the max.

Single engine performance: Believe it or not the single engine climb rate and ceiling on the P337 is better than any unmodified piston twin. Some of the Riley and RAM (father and son by the way) Cessnas will climb as well as P skymaster on one engine, but even they will do it with quite a bit of drama and at a higher airspeed and lower climb angle than the P skymaster. The Riley Super Skyrocket P337 with 310hp engines will outperform anything but a turbine powered twin on one engine (especially when considering climb angle). I only had one occasion to actually fly on a single engine, although I practiced it many times. Once I had one of the metal fuel injection lines on the rear engine crack completely in two. The only indication I had of a problem was a sudden large increase in fuel flow. I was so unconcerned about flying on one engine that I elected to shut down the rear engine even though I really didn't know if there was anything seriously wrong (might have just been the guage or line to the gauge). I flew 20 minutes back to my home field with no drama whatever. When I oppened the cowling I saw that fuel had been pouring out all over the tops of the cylinders at high pressure though a completely severed solid steel fuel line. I have no idea how it broke, probably a manufacturing flaw, but it could have been a disaster if I hadn't shut it down.

Engines: I never had any issues with the TSIO360c/d but they do have a low 1400 tbo and it is quite common to not make even 1400. Many people claim that there are extra problems on the rear engine due to overheating, but I have never seen this. The only problem I had was never engine oil leaks from the rear engine. It may have even been simply oil coming from the breather (I had a tendency to keep the engine topped up in oil), but it wreaked havoc on the rear deicing boot. The rubber on those boots muct have been designed in the 1930s becasue it swelled up like latex when it got even a hint of oil on it. The boot is expensive so you don't want to be replacing it every year, I assume there is an answer but I never found it. I don't know what people were doing to the engines on P337s to cause them to need overhauls at 300 or 400 hours, but I saw many P337s that required overhauls at those intervals. At the time I owned the P337 I was a B-52 pilot and used to following strick proceedures so maybe I was more conscientous regarding turbo cooldown, rapid power changes, leaning and cowl flaps, than your typical owner, but whatever the case the engines were trouble free (other then the rear engine oil leak).

Cabin: The cabin in the P337 is about the same as a P210. Certainly not what anyone would call cabin class but a decent 4 person plane with a reasonable amount of baggage. The one issue with the P337 vs. a plane like a 210 or other large single is that they is no room behind the rear seats (if you have all 5 in) Since the engine is behind the seats the only baggage space is in the main cabin. I remember comming back from Mexico with my wife and 2 friends with so much stuff in the cabin that the rear seat passengers had to sit on top of it. The useful load and CG range was great (1500+ lbs) so even with full fuel (750 lbs) you could legally fly with virtually anything you could fit in the cabin. I could not come up with a realistic scenario that would have the plane out of CG range.

Handling: The USAF used these planes a FACs (Forward Air Control) and those guys beat the heck out of them. The planes were often overloaded so badly that they wouldn't even maintain altitude on one engine. In addition the pilots had come out of pilot training where they flew planes with 6.66 and 7.2 g limits (T-37, T-38), so they were used to yankin and bankin. I have heard that the issues with the wing spar on the 337 came from experience with spar failures on USAF 0-2s, I don't know if this is true but it would make some sense. In any case, since I had spoken to guys who had done some acro in their O-2s (and there was a guy actually doing a routine at airshows in a skymaster at the time) I decided to try it in my P337. Aileron rolls were easy with just a few degrees nose up prior to the start and ending a few degrees nose low. I did not have a G meter so I was unwilling to try a loops but I am sure it would be possible to do one without an over g, but I would very much not recommend it to anyone not extremely familiar with acro in a wide range of aircraft.