The Art and Fun of Collecting Aircraft Engines
by Graham White
Collecting aircraft engines is not one of the easier pastimes to follow. However, it is by far the most satisfying. It seems that the more difficult a task is to accomplish the more satisfying it becomes. With this thought in mind, collecting aircraft engines is the most gratifying hobby one can imagine.
Of course, this pastime is fraught with problems and, to use the euphemistic buzz term of the times, the most challenging. Converting a derelict hulk into a pristine and running example of what represents the pinnacle of mechanical engineering is rewarding beyond belief. Before jumping off into the deep end, some fundamental questions need to be answered: what type of engine to start with - air cooled radial, liquid cooled Vee or flat spam can engine? Then, how much should one pay for one of these jewels?
After the acquisition of an engine the collector needs to decide if this engine is going to be a runner (highly recommend), or a static exhibit (boring). Then an accommodation needs to be found to work on it. A garage is usually more than adequate. A build stand, special tools and/or equipment are other thing to keep in mind.
The best deals on engines are the "oddballs" or those with little or no demand. As an example, some of the small Spam Can engines such as the Lycoming O-360 series demand astronomical prices considering how rude and crude they are. On the other hand, a large and complex masterpiece such as a Pratt & Whitney R-4360 can be obtained for little more than scrap value. How many R-4360 powered aircraft have you seen on the local airport ramp lately? Another good candidate for excellent value is any early "B" series Pratt & Whitney R-2800. On several occasions, the author has been asked to take away a B series R-2800 because it was taking up too much space. And we are talking about complete, runnable engines, albeit in run out condition. It may come as a surprise to know that the legendary Rolls-Royce Merlin can be acquired for a relatively low price, provided it isn’t a desirable dash number. As an example, a Packard built dash one can be purchased for less than $5,000.00. However, a dash nine is worth upwards of $150,000.00. The only down side to the scenarios described above is the fact even oddballs are now climbing in value - so now is the time to buy.
Where to buy? A number of avenues are available. The "Engines of Sale" section of Trade-a-Plane is one good source. If you live near a large metropolitan area, there’s a good chance an overhaul shop is nearby. Often times the shops that overhaul engines will have a couple of engines that have very little demand and they would be than more than happy to unload it. This is especially true of some of the larger radials such as B series R-2800s, certain dash numbers of the Wright R-1820 and Wright R-3350. Of course, the engines mentioned here are large and heavy. This brings up another problem - logistics. How on earth do you move these things around when they weigh upwards of 5,000 pounds. Most shops will have a fork lift to load it into the bed of your pickup. If it will not fit, a car trailer is usually a good bet.
If it is planned to restore the engine to running condition caution needs to be exercised in checking its internal condition. This is a relatively simple process. Most engines will have some form of oil screen or filter. Many US built ex-military or large commercial engines have a Cuno filter. Since removal of this filter or screen is a regular maintenance chore, examination is easy. The purpose of removing the filter or oil screen is to check for metal particles. With a runout engine it’s not uncommon to see a small amount of metal such as copper or silver, however, any visible metal should be no larger than a grain of sugar. If the filter is full of ground-up metal then forget it, this one is not worth messing with. Repairing the damage of a catastrophic failure simply isn’t worth it. Furthermore, in the case of the larger radials, sophisticated and special tooling will be required to completely disassemble the engine. A word of caution when removing the filter or screen, the oil contained within it probably has many hours accumulated since it was last changed. Nothing stinks or looks as nasty as aircraft oil with about 1,000 hours on it..!!
Once your engine has been purchased, thought needs to be given as to how it needs to be worked on. Some kind of build stand or QEC (quick engine change) will be needed. Another fundamental question is to what extent does the engine need to be worked on. With the smaller radials such as Continental 220s, it is easy to tear them completely apart without the use of too many specialized tools. With the larger radials such as the Pratt & Whitney R-2800, it would be impractical for the average amateur collector to tear it completely apart. However, removing cylinders, ignition systems, nose cases and blower section is easy, albeit laborious. Tools for removing cylinder base nuts will be needed but they are easy to make. Gland nut wrenches for pushrod gland nuts are still available at reasonable prices. In the case of a Merlin, again, it is relatively easy to remove ignitions systems, intake manifolds, blower sections, wheel cases etc. However, with a Merlin, when it comes to removing the cylinder heads and cylinder banks, specialized tooling in the form of "bank jacks" is necessary.
The erstwhile engine restorer will be faced with what appears to be an insurmountable task. Fear not, just start pecking away at your pride and joy and before you know it, most of the major components will be removed. At this point it will start to take on the aspect of being a doable project. During the disassembly stage, it cannot be emphasized enough to take lots of pictures. Film is cheap, waste it, take as many photos as you can. Every detail should be documented with a picture. Even with overhaul, maintenance and parts manuals, it’s surprising how invaluable "your" pictures will be.
Mentioning manuals brings up another good point. Purchase every manual available for the particular engine you are working on. Original manuals will probably be out of the question and even if you could find originals, in most cases, it would not be a good idea to use a valuable and collectable manual as a working document covered in oily finger prints. Several companies specialize in selling photo copies of manuals albeit poor quality fourth or fifth generation. However, one of the best-kept secrets in the world of manuals is the National Air & Space Museum in Washington DC. If NASM does not have the manual you need, then it’s not worth having. Their copying fees are very reasonable and unlike the commercial operations that peddle these documents, NASM’s are first generation copies and consequently the quality is superb. In fact, often times the copies look better than the originals.
Prior to turning a wrench on your recently acquired pride and joy, it is highly recommend to read the manuals cover to cover. If you have never worked on an aircraft engine before, be forewarned, this is a very different ball game from working on a car or motor cycle. Aviation is totally intolerant of slap dash workmanship; the kind of thing one can sometimes get by with in the automotive world. The first thing that will strike you when tearing into one of these engines is the superb workmanship, attention to detail, expensive manufacturing techniques and quality of materials. If you have worked on a high performance race engine then the innards of an aircraft engine may look familiar, if not, be forewarned, these engines will not tolerate ham-fisted mechanics.
In all likelihood the engine purchased will be in less than ideal cosmetic and mechanical condition. Rather than get overwhelmed, treat each component as a stand-alone project and the entire engine is simply a series of mini projects. Half the battle is waging a physiological battle with one’s self. If you are working on an eighteen cylinder radial, for example, treat each cylinder as a project; removal, cleaning, lapping in valves, painting...etc. In this way, it is remarkable how easy it seems.
Once the engine is complete, this is only half the battle. Some form of display trailer will be needed. In addition to the trailer it will be necessary to take care of the following items; propeller, oil tank, fuel tank, fuel pump, control panel, fuel lines, oil lines, fuel priming system. In addition to the foregoing list, items such as a pre-oiling system or a fuel transfer pump may be nice things to have. The display trailer is basically an "L" stand on wheels with a tow bar. Of course, it needs to be street legal so items such as lights and brakes will be necessary. Software for designing something like a trailer is now so cheap it’s not worth trying to sketch it on the back of a napkin.
It’s highly recommended that all components such as fasteners, hoses, clamps, etc., are of aircraft quality. As an example, nothing looks more out of place than a plastic tie-wrap used instead of an Adel clamp. It would also be nice if an aircraft engine mount is used. If a correct mount cannot be found, it’s recommended that a mount be fabricated that, at a minimum, looks like an aircraft engine mount. It still amazes this writer that museums display engines on mounts that are typically pieces of angle iron cobbled together just to support the engine. If the engine were mounted on a correct aircraft mount on an "L" stand, the display would look infinitely more impressive. But then, the way museums handle their engine is whole different story. Fuel and oil tanks can be easily fabricated from compressed air tanks, the ones you see in auto parts stores. They will need fittings welded on for a gas cap and oil filler. In addition, the oil tank will require fittings for oil out to the engine, oil return, oil line to the pre-oiler and a breather line. The fuel tank will need, in addition to the filler cap, the line that goes to the engine driven fuel pump, a smaller line to the primer pump and a vent.
A control panel can be a relatively simple one housing; starter switch, left and right mags, pre-oiler switch, boost coil switch, fuel transfer switch...etc. Gages can be purchased very cheaply. During World War II, aircraft instrument dials were painted with a radioactive luminescent paint. The unfortunate down side to these instruments was the alarming incidence of throat cancer for the female workers who painted the numbers by hand with very fine camel hair brushes. In order to keep a fine tip, the women would lick the brush not realizing the hazard they were exposing themselves to. Of course, manufacture of these instruments has been banned for many years, however, they are still available at dirt cheap prices. The danger of the radioactivity is minimized due to the glass dial. But no instrument shop will touch these gages - literally and figuratively.
For a supercharged engine it is recommended that the following instrumentation is used: manifold pressure; oil pressure and tachometer. If the engine is liquid cooled, a coolant temperature gage is needed. If you have an air cooled radial, then a cylinder head temperature gage is required. Controls will be needed and, depending on the complexity of the engine, can simply be a throttle. Or, in the case of a more complex engine, throttle, propeller, mixture and blower shift will be needed. One of the better set-ups is the Douglas AD Skyraider throttle quadrant. This unit is a flat rectangle and therefore easy to mount on a control panel. Additionally, the Skyraider throttle quadrant has throttle, prop, mixture and blower shift controls.
Depending on what type of engine is being worked on, propellers can be quite cheap. US engine manufacturers use standardized propeller shaft spline sizes. Higher horsepower engines (those over 1,000 hp) have what’s known as an SAE 50 spline or SAE 60 spline. The 50 spline shafts are used up to 2,000 horsepower and 60 splines are used in engines capable of producing 2,000 to 3,500 horsepower. A couple of rarities have 70 spline propeller shaft but these are in the small minority. The two major manufacturers of large propellers were Hamilton Standard and Curtiss Electric. Some Hamilton Standard 50 spline and 60 spline propellers can be purchased for scrap value. As with everything else, supply and demand dictates price. As an example, a 50 spline Hamilton Standard propeller for a Merlin installed in a P-51 Mustang will sell for upwards of $100,000.00. And yet, a 50 spline prop removed from a DC-3 can be purchased for less than $300.00. Likewise, a 60 spline prop from a DC-6 can be purchased for less than $300.00.
Curtiss Electrics have all but disappeared from the face of the earth, consequently, their value is typically in the stratosphere. Working on propellers is not for the faint of heart but it can accomplished by any "wrench" of average skill. Again, manuals are a must, otherwise, you are faced with a million bits and pieces with no idea where they go and how they should be fitted. However, if you live near a prop shop that has experience with these large Hamilton Standard props, it’s recommended that you let the pros do it. Due to their massive size, it’s often advisable to cut down the diameter of the prop. It is still possible to put a heavy load on the engine even with the cut down prop. As an example, the author has a DC-3 prop reduced to eight feet diameter mounted on a dash one Merlin. This engine has been run up to 60 inches manifold pressure and 3,000rpm. The governor simply cranks in more pitch when the load is sensed. Like the US, England also used standardized propeller shafts, in their case SBAC or Society of British Aircraft Constructors. The larger SBAC props are not as readily available as their US counterparts.
The fact that these restored engines will never fly gives the restorer a lot of leeway not afforded operators of airworthy engines. For instance, it really does not matter what prop is mounted as long as it will fit. Various components from other engines in the same family can be fitted which otherwise would not be allowed. For instance the author’s Merlin has dash seven valve covers even though it is a dash one engine. Accessories such as engine driven fuel pumps do not have to be of the same specification required for an airworthy engine. As long as the requirements for fuel pressure and delivery rate are met, it doesn’t matter. Exhaust systems offer the same flexibility. The author has a Pratt & Whitney R-2800 removed from a Curtiss C-46 and yet it sports Douglas A-26 exhaust stacks
Running these engines represents a different article - so stay tuned..!!!