Going for Gold
PUBLISHED: 11:42 04 April 2012 | UPDATED: 14:12 10 October 2012
Two thousand two hundred and thirty-nine cubic inches (36.7 litres) dual overhead cams, forty-eight valves, twenty-four sparkplugs, a very large two-stage/two-speed supercharger, contra-rotating propellers and the mighty PR-100 carburetor make for the largest and most powerful V12 engine ever to power an airplane - period...
Two thousand two hundred and thirty-nine cubic inches (36.7 litres) dual overhead cams, forty-eight valves, twenty-four sparkplugs, a very large two-stage/two-speed supercharger, contra-rotating propellers and the mighty PR-100 carburetor make for the largest and most powerful V12 engine ever to power an airplane – period.
The Rolls-Royce Griffon has its origins in the model ‘R’ engine that powered Supermarine’s Schneider Trophy racers. It is not an upgraded Merlin−the Griffon and the Merlin come from very different backgrounds and their family trees are quite individual, even though they are both 60º V12s. The Griffon was meant to replace the Merlin in certain installations and was used on late-model Spitfires, Seafires, all the Spiteful and Seafang series aircraft as well as on certain one-offs, such as the Martin Baker MB5. The most common installation, however, was in the Avro Shackleton maritime reconnaissance aircraft. It turned out that the loitering mission suited the Griffon very well, and it was the only V12 to remain in service up until 1990.
Precious Metal is a heavily-modified North American P-51D Mustang. It has clipped wings, a cut-down turtle-deck with the pilot seat moved aft about 18 inches, a P-51H tail and is, of course, completely custom, firewall forward. There are hundreds of smaller mods throughout the airframe, which are all necessary for this one-of-a-kind racer to accomplish its mission. Precious Metal was conceived with only one purpose in mind: speed. It’s not good for anything else. It’s not a nice airplane to fly. The visibility is preposterous. You can only move your head in the cockpit about one-and-a-half inches either side. Forward visibility is of course non-existent until you exceed 300mph−but seeing forward is over-rated anyway, and in racing would be considered cheating. The cockpit gets very hot. You cannot taxi on a 40-foot taxiway without a wing-walker since the canopy has to be closed while the engine is running. You can never let go of the controls in flight, as the airplane is unstable. The systems are very complex and require constant monitoring. It requires special servicing and mechanics. The carburetor, being designed for the larger R-4360, does not allow the engine to idle any lower than 1,100rpm, which means you are constantly riding the brakes during taxi. The instrument layout is probably the worst I have ever seen in any warbird, and the ergonomics in the cramped ‘office’ would be rated unacceptable by any test pilot. With all that in mind, is it an experience one should really strive for? Absolutely! Pylon racing is by far the greatest thing a pilot can experience, especially in the coveted Unlimited class.
Unlimited racing has a couple of basic rules: the aircraft must be piston-powered, propeller-driven and weigh at least 4,500lb. There are various other safety rules – for example, the requirement of an oxygen system in case of smoke in the cockpit.
Naturally, WWII fighters dominate the field as they represent the pinnacle of piston-engine aircraft development. (Had the jet engine not arrived when it did, we would have seen even greater achievements in the development of reciprocating engines after the war, but this was not to be.)
Some people argue that it’s sacrilege to chop up a precious historic relic for the purposes of racing. You may be surprised that most of the racing community would agree with that notion. It turns out that no one has chopped up a Mustang for this purpose for well over twenty years. Most highly-modified racers were built from crashed hulks and spare parts, and have much more history as racers than they ever did as fighters. Chances are, they wouldn’t even exist if it wasn’t for racing. There is only a handful of purpose-built racers in the field; the rest of the machines that appear at the races are basically stock airplanes.
2,450 horsepower not enough...
Now to more details on the engine: the Griffon 57A was the last in the series of the mighty V12 designed for the Shackleton. It was originally fuel injected and had a single-stage/single-speed supercharger, capable of 80in Hg manifold pressure at a rated takeoff rpm of 2,750. This would produce 2,450hp. That’s nearly 1,000 hp more than the stock Mustang-assigned Merlin. “But how can you achieve 80in Hg on 100-octane fuel without detonation?” you ask. You cannot: the engine had an ADI (Anti-Detonant Injection) system operating anytime you exceeded 45in Hg.
ADI fluid consists of a very corrosive mix of 50 per cent distilled water and 50 per cent methanol. It lowers the temperature of the intake charge and enables very high pressures going to the cylinders without catastrophic detonation. Even with all this, the stock Griffon would not be enough to propel a Mustang to winning speeds: you can quite easily get the same kind of power out of the lighter Merlin, so modifications are required. Of course the standard porting, polishing and balancing techniques used by any hot-rodder are required, but the fuel injection and stock supercharger have to go−they would not be capable of pumping enough fuel and air to support a thirsty monster-machine like Precious Metal.
The intake elbow was rotated 180 degrees to accommodate the PR-100 down-draft pressure carburetor. This puts the intake on top of the engine, unlike the Merlin and stock Griffon. This is handy for several design reasons: it keeps the intake high, and since we don’t use any air filters it helps avoid ingestion of foreign objects and makes the entire installation much more aerodynamic. The supercharger was replaced with a much larger unit from a Griffon 74: the same engine you would find on a Fairey Firefly. This unit is capable of producing an astonishing intake pressure of 140in Hg! This is much too high for conventional fuel, even with ADI, which is why we run specially-formulated 145 or 160 Octane VP racing fuels, depending on the power settings used. There are many other mods, including extra oil pumps and galleries to keep the thing cool and lubricated. Stronger valve springs are installed to prevent valve bounce at higher than rated rpm and so on. Building a race motor is something between an art and a science. The hybrid power plant I’ve been describing was built by Jeff Neff and was originally designed for the Miss Budweiser hydroplane race boat series. (Here, the mighty Griffon even defeated the turbine-powered competition for several seasons before it was finally retired in the eighties.)
Racecar driver and Le Mans winner Don Whittington combined the spectacular powerplant with the P-51 airframe in 1989 in Ft Lauderdale, Florida. The airplane was built over a surprisingly short period of nine months and made its debut at Reno in September that year.
Precious Metal has had a checkered racing career, including an engine failure followed by a crash landing on a riverbed during a heat race start in the nineties. At that time, the propeller acted as a giant airbrake when the engine failed as the feathering system had been removed. As soon as I got my hands on the airplane, however, we installed a new feathering system−just in case. It’s a constant research and development project to make a racer fast and success does not happen overnight: it takes years of trial and error. Precious Metal has yet to show her true colors in a race, but it will happen…
Inspired by a magazine article
In late 1979, I was a seven-year-old boy growing up in Sweden, and I got my hands on a flying magazine called Flygrevyn. It had an article about the Reno Air Races and a series of pictures of Steve Hinton Sr flying the Red Baron, another Griffon-powered Mustang. It was the coolest thing I had ever seen! I had no idea air racing even existed. I probably read the article two dozen times. I already knew that I would fly something when I grew up, but that’s when I decided that I wanted to race airplanes. Pretty much everything I’ve done since has taken me closer to the goal of racing ‘Unlimiteds’ at Reno. I flew professionally for twenty years before I had the first opportunity to race an airplane. I bought a Cassutt named Miss USA and entered as a Rookie in 2008. It was an incredible experience. The following year I piloted two Formula Ones. We went on to win the Gold and my first Breitling watch with a second Cassutt called Invictus, and won the Silver with Miss USA in the same year. The air race historians told us that had never been done before. We had to retire on top and decided to move on to racing jets in 2010. I finally got to go fast on the big boys’ course in a TS-11 Iskra-jet called Pole Dancer. Lots of fun and an excellent experience, but I had other goals in mind. Precious Metal had been in storage for a few years after its second owner, Ron Buccarelli, retired from air racing. I had been trying to convince him to let me bring the airplane to Reno. Finally in May 2011, together with a couple of friends, we got our hands on the prize. We convinced Ron and his business partner to let go of the airplane and we were on the way to the Unlimiteds!
It took a lot of work to make the airplane ferryable. Machines don’t like to sit for years, so this was a huge undertaking. We realized very quickly that we had to separate the list of things that needed to be done into two parts. First, make it safe to fly, take it to Pylon Racing Seminar (PRS) in June, then over the summer, go through and make it fast. Another complication was that I needed to have fifty hours on type before I could attend PRS. We had a month before I needed to head west.
After the condition inspection it was time for the first test flight. I had never flown this beast before and there was a lot at stake. How do you get the training to operate a single seater of this caliber? Simple: the good old North American T-6 is the answer. It was the trainer for all the single-seat fighters on the allied side in WWII. Good enough for them, good enough for me. I had the advantage of having instructed in T-6s for fifteen years, so the step wasn’t that big. Or so I thought… I had done my qualification flight in the T-6 with Buccarelli and he had told me everything he remembered about flying Precious Metal from years earlier. However, Buccarelli wasn’t available the day we came to pick up the airplane, so I was on my own. After a very extensive preflight and sitting in the cockpit for about an hour getting familiar, it was time. Master on. “Clear!” Starter engaged. Boost-pump on and tickle the primer while turning on the mags: I’m starting to run out of hands here... Oil pressure, check. The motor cranked up OK and I knew it would heat up quickly, so I made my way down to the other end of the field. I ran it up just like any other piston airplane and went left to right in the cockpit twice to make sure every lever, valve and switch was in the right position−there are a lot of them. Without ADI, we only use 55-57in Hg for takeoff. Even with this reduced power setting the airplane accelerates very quickly. The instrument panel in this machine leaves a lot to be desired. It’s all old-school steam gauges−however, they are not in any discernible order. Forget the standard T pattern: it’s almost like someone collected the various gauges required, threw them in a bucket, rattled them around and then tossed them all round the panel. It makes no sense whatsoever and leaves a lot to be desired, but there’s no sense complaining.
The airplane is surprisingly unstable below 100mph, squirrely even. It turns out that the proper way to fly this machine is to keep the tail on the ground and use the tailwheel steering until the rudder effectiveness is sufficient, which is around 100mph.
Nearly caught out on first takeoff
As I accelerated down the runway, the mechanical tachometer started catching up. The sound was deafening. The tach skips in delayed increments of around 150rpm at a time – a very poor design. Obviously I was looking at pressures and temperatures, and worrying about the engine−but I realized as I was rotating that the engine was overspeeding. Dammit! I reached for the propeller lever and nothing happened. I couldn’t believe I was about to blow this thing up on the first test flight. If I throttle back I’ll be in a cornfield, but it can’t be healthy to continue what I’m doing... Doing a quick scan as I brought up the gear, I tried to diagnose the problem as we accelerated through 200mph in the climb.
This airplane is equipped with a T-6 style throttle quadrant – something I have thousands of hours’ experience handling. It turned out that ‘negative transfer’ had occurred: in a T-6, the throttle lever is on the left, the mixture in the middle and the propeller on the right. Not what the rest of the world standard is, but it was designed before standardization. In Precious Metal, the prop is in the middle and the mixture on the right. No one ever bothered to remove the ‘M’ and the ‘P’ from the respective levers (although they were labeled correctly). The first takeoff in a new machine, to quote a friend of mine, is “like drinking from a fire hose.” Too many things going on at once... Information overload is something we have all experienced in training. I sorted out the problem, brought the prop back, increased the mixture to full rich again and continued my circling climbout: back to the task at hand!
The airplane is completely unstable in pitch. It’s a very strange sensation, which would be unacceptable in any other machine. In pitch, it’s a bit like flying a helicopter−except you have divergent control force reversal. The ailerons are heavy and sluggish, providing a roll rate no greater than that of a Stearman. Rudder? Who needs it! We have contra-rotating propellers, baby. The rudder trim, although installed, is never used−regardless of speed and power setting. The contra-rotating propellers makes the airplane fly like a jet, almost like it’s on rails. Once satisfied that the airplane would stay running, I set off for home. It was only a 70nm flight back to Kissimmee, but I did some stalls and general handling exercises on the way home to prepare for what I thought would be a demanding landing. I arrived in formation with my escort, a twin Comanche. There was a large crowd gathered at the Kissimmee Air Museum. We had invited them for a surprise, but none of them knew what we were bringing home, and nor did they guess correctly. Lots of rumors were flying, but no one nailed it!
I set up for the landing and the gear came down OK, as did the flaps. I better touch on the threshold, this thing is fast... It turned out to be an absolute pussycat to land. It didn’t use as much runway as I expected either. Phew! It was a pleasant relief after the takeoff experience.
2,200 miles, hand-flying all the way
As the final paperwork for the transfer of ownership didn’t come through until two days before the Pylon Racing Seminar started, stress levels were extremely high. With the paperwork issues resolved, I set out on the 2,200nm trip to Nevada. It was an absolute chore: single pilot, no autopilot and in an unstable airplane… Not a pleasant experience.
The trip went well, although I had some minor maintenance issues and the engine was running hot− very hot. The Griffon was originally equipped with an intercooler and a cooling jacket in the supercharger. This had been removed since we had ADI instead, and the part of the radiator that normally services those systems was now being used to increase the capacity of the main cooling system to handle the high thermal output at race power. ADI is not used for low power settings, and here intake temps get hot−even more so with 104°F ambient temperatures in Arizona.
I made it to PRS and actually took the check ride for the P-51 type rating with John Penney with exactly 50.0 hours in the logbook. The program started that afternoon−but I wasn’t happy with the performance of the airplane. It was way too hot, lacking power and generally not happy. It turned out that we’d lost a camshaft lobe, so we had to replace it before the trip back home. But we passed and would be able to fix the other issues over the summer.
During the summer, we tore the airplane apart in Kissimmee. The engine came out; we overhauled the supercharger, re-sealed the heads and banks, replaced cams and rebuilt every system in the airplane. The ADI had corroded everything: we took the tanks out and re-plumbed all fluid systems. The spray bar water tank wasn’t big enough to cool the engine at continuous high power settings, so we had to switch fuel and water tanks. The radiator and oil cooler were overhauled and many other things were gone through and repaired. The airplane was test flown a few days before it was time to leave for the races. It took several months of eighteen-hour days to pull it off. Everything worked great and all of a sudden the airplane had been transformed in to the fire-breathing monster I had always hoped for. At the same climb power setting I had used previously, the climb rate went up by 1,400fpm! The difference in power is amazing when you set the engine up the way the Rolls-Royce manual recommends…
Three emergency landings on the way...
The trip to Reno, however, was the worst cross-country I have ever been on. To cut a long story short, I made it there in seven days (not the planned one and a half) after three emergency landings due to: loss of oil pressure; studs pulling out of the engine case; and one of the camshaft drives skipping and breaking a tooth. The nightmare of getting the airplane to Reno in time is worthy of a novel−let alone another article. Thankfully, a very dedicated gang of volunteers showed up out of nowhere in west Texas: Brett, Nathan, James, Jason, Charlie, Monty, Kelton, Neil and Pete. The welders and machine shop consisted of father and sons Jim, Michael and Eric: they welded the engine case back together just in time for us to arrive in Reno for the tech inspection. What an unbelievably dedicated group. The cult following of Precious Metal reaches far beyond the grandstands in Reno.
My team – Maggie, Phil, Brenden, Mike, Scott, Michael, Eddie, Don, Heike, Andy and Ron – were all anxiously awaiting our very late arrival, and several other teams dedicated their members to help us get ready in time. We passed tech just in time to take off for the last qualifying period with fifteen minutes left on the clock to qualify.
This was the first test flight on the new ADI system, so we only ran 70inHg at stock rpm as per Mike Nixon’s direction. This gave us a qualifying speed of 399mph−and that was with traffic on the course. But I couldn’t complain−we had posted a time and started in 11th place out of 27. There were three provisional entries that would have taken my place had I not qualified in time. It would be easy−and, frankly, a lot more fun−to work our way up in to the Gold heats anyway.
We flew two heat races and worked out a few small cooling issues. By Friday afternoon, everything was running brilliantly and we were set to do great things on Saturday and Sunday. We were absolutely on top of the world−and this was something I had been working towards for 32 years. We expected a fantastic weekend, but then that horrendous accident happened. On friday night, the Galloping Ghost, piloted by Jimmy Leeward, crashed in to the box seats killing him and ten race fans. The races were cancelled for the rest of the year.
Terrible to fly, awesome to experience
Flying Precious Metal represents both the best and worst aviation experience I have ever had. Terrible to fly, but awesome to experience. It is a culmination of huge sacrifices and great feats by my crew – and to call it an emotional roller coaster is an understatement. Be very selective with what you allow your seven-year-old to read. You never know what strange adventures it may lead to…
Precious Metal can be seen on public display at Warbird Adventures’ Kissimmee Air Museum in Kissimmee, Florida, when she’s not out on the road pursuing a checkered flag.
Words ~ Thom RichardPhotos ~ Keith Wilson & Neal Sands