Hello Kevin:
To answer your question, I am the Ray Torres from RT Aerospace. I was browsing through your web page yesterday and saw the comments concerning our baggage door mod, which I would like to comment on. I'd appreciate it if you could post this on the message board.
Before getting into the mod I would like to give you some background on myself and my company. I have a degree in Aerospace Engineering and am an FAA Designated Engineering Representative (DER) in structures. My company's main business is providing engineering support for aircraft structural repairs and modifications, primary to the airlines and corporate aircraft. Over the past twenty years we have obtained between 70-80 STC's for our customers.
I bought my first 337 in 1989 and have since owned/overhauled/rebuilt a 1965, 67 and 73 Skymaster. All of the mods I have done on Skymasters (except for the P337 door) were done because I had a personal need for that modification in my aircraft. The ability to sell to mods to other 337 operators has never been my primary intent although it does help to justify
some of the mods.
RT Aerospace has two STC's concerning retrofit of baggage door on 337's. STC SA01344AT installs a baggage door on P337's and STC SA0188AT installs the door on non-pressurized 337's (post 1973).
When I got into the baggage door mods I thought that the response from skymaster owners would be overwhelming since this modification gave access to the back of the airplane which is all but useless without the door. Unfortunately, this hasn't been the case, and except for the two prototype aircraft, no other aircraft have been modified. I can't explain the lack of interest in the mod and I don't feel its the price because in both cases
they were initially priced under cost. The only thing I can acertain from reading the comments on the message board is that people have alot of mis-conceptions and fear about pressurized aircraft. Actually, the only difference between a P337 and a non "P" 337 is one additional frame at the pilots side window and about 20 lbs of tank sealant.
With the regards to our modifications, the pressurized door installation is much more complicated than the non-pressurized, but there is nothing "scary" about the installation. Both installations use the same door, which is a epoxy-glass/carbon fiber layup with a 1" thick nomex honeycomb core. Door dimensions are about an inch smaller than the Cessna installed door on older skymasters. On the P337 installation, the door has a piano hinge along the top edge and a 3-pin overcenter latching mechanism along the other 3 door sides. The door opens up and has a hold open rod to hold the door out of the way when loading. Sealing of the door is accomplished through a blown seal which tees off of the main cabin door installation.
In order to satisfy the FAA, the door and latching system was tested/cycled in a mockup frame to ultimate pressure differential. We stopped the testing at over 10,000 cycles with no failures or damage.
The fuselage modification for the P337 aircraft consists of the installation of two stub frames at the door forward and aft edges and an upper and lower jamb. An external doubler is then installed which spans from the aft pressure bulkhead to forward of the main gear frame. Again, in addition to the structural analysis of the modification, the FAA made us test the installation to limit pressure differential. This was done on the ground with an external pressure source. The biggest problem we encountered during this test was not with our installation, but with numerous leaks at the main entry door. I was extremely difficult to reach limit pressure differential. The prototype aircraft was a 1973 P337 so the fuel valves were still up in the wing. Modification of a 76-78 P337 will require relocation of the fuel
valves. In addition the bench seat tracks would have to be modified and the seat aft travel limited due to its proximity to the door area. Probably the best modification for these aircraft would be to remove the bench and install floor track mounted seats as in older skymasters.
The non pressurized installation differs in that the only modification to the fuselage is the addition of a door seal retainer. The added door is hinged on the forward side with two external hinges and a paddle latch on the aft side provides the latching mechanism. This installation is very similar to that installed by Cessna on pre 1973 skymasters.
If any body is interested they can e-mail me and I'll put them in contact with the owners of the two modified aircraft.
By the way, we are in the process of modifying our price list, and the new price for the P337 door installation will probably be in the
$20,000 -25,000.00 range depending on model year.
As I stated before, I'm very impressed with your web page and I hope to be looking at it on a regular basis.
Regards,
Ray Torres
RT Aerospace
Ray's email is
rtaero@bellsouth.net. (KM)