I received a very interesting question from a reader who requested to remain anonymous, which I am happy to do in this case. His question is one that deserves a response and also one that I believe many aircraft owners would be interested in:
“Hi Paul, I stumbled across your reply to a question from Ajay on adding turbo to a Piper Cherokee 6 (Can I upgrade to a turbocharger?).
“Can I tempt you with a more specific scenario? I have a 1972 Cherokee 6 with a Lycoming IO-540-K1A5 engine. I’m looking for more altitude out of my bird to give me more options in getting above weather.
“Rajay offers a turbo STC for the Lance’s IO-540-K1G5D. To my non-expert eyes, the differences Lycoming lists between the -K1A5 and the -K1G5D (mags, injectors, fuel pump) don’t clearly scream that the former is unsuitable for turbo.
“My question is that I plan to call Rajay and ask if the company could be persuaded to seek an STC for the -K1A5 in the Cherokee 6 airframe.
“Is there anything fundamentally crazy about asking them to seek such an expansion of the STC? Is there any fundamental barrier to that?
“Thanks for any thoughts!”
A few days later, we received this from the reader:
“Hi Paul, you can retract my question. I got it answered by Rajay. The double realities of heightened FAA review standards and the increased cost of small batch manufacturing mean that not only is it prohibitively expensive to get a new STC approved, but it’s too expensive to continue to manufacture the ones that are approved.
“I assume other complex STCs face the same issues and the implications of this are pretty significant on general aviation. Major STCs are fading away for GA.”
I found this all very interesting and thought I’d contact Rajay Turbo Products myself to discuss the issue.
I had a very nice chat with Tom, who has owned Rajay for the past seven years, and he confirmed what our reader stated.
Tom pointed out a fact that many in the GA industry have learned over the past several years: Things have really changed from the “heydays” of the 1960s and 1970s.
If we look at the production of GA aircraft these days, we all know that the quantities are low and will never reach the numbers we produced decades ago.
Tom hinted that a turbo kit at today’s prices would be at least $50,000 to $60,000 just in parts. When you add the installation costs, you’re talking some serious money.
As Tom pointed out, manufacturers have extreme difficulty in securing suppliers to produce products because of the small quantities and the high-quality standards that are required in the aviation industry. Sadly, we are a victim of our own circumstances, which we will never outlive.
Even though there are no new kits available, Rajay is still committed to supporting all users of its products, Tom emphasized.
Getting back to the original question, I believe the key answer here is even though it is a reasonable idea, it just is not a smart move financially.
I might add that, even if there had been an STC for this aircraft, I don’t think it would have been a wise investment because I doubt very seriously if you could recover the investment cost of converting a normally aspirated Cherokee 6 to one with a turbocharging STC when you are ready to sell the aircraft.
I’d like to thank the reader for submitting his question before pursuing his idea of modifying his engine. There is no doubt that before jumping into any major modification, it’s best to spend the time doing your research and asking a lot of questions.
Airplanes are a little less likely to end up being shut down with the body of the turbo at high temperature for a simple reason. It’s hard to descend, touch down and taxi while asking the engine to produce a lot of power. In most cases gradual power reductions have allowed the turbo body to cool down rather effectively especially the time spent in descent with ample cooling airflow through the cowling, decreasing EGTs, and continued oil flow through the center section. Actual measurements have demonstrated this from at least two sources, one of which was George Braly himself. The numbers showed no additional cooling during a post flight extended idle. If the decent was typical an extended idle was a waste of time and gas and might even lead to higher lead deposits because of the combustion temperatures at idle.
I once had a car with a turbo. I did not know it had a turbo when I porched it. It was an older car. It surprised me when this car was trying to pass me & cut me off at the sesame time. The little cat turned into a rocket when I gassed up. This surprised me. I stopped up at a friend’s gas station. to get some gas. I asked him how the little could take of so fast. he said it was turbo charged. Then he said you just cannot shut it off. He said you have to let it
idle for a few minutes. The engine & turbo has to cool down. Before you can shut it off.
So, in a plane do you want that. Cars are liquid cooled. planes are not. I stayed away from
turbo from then on.
Good thing there are no essay questions on the PPL written.