Why was the IO-720 a failure?

[GeeBee]

I thought a review of the sales brochure might be in order. I've had this since I was 11. The Golden Age.

 

[Cody Stallings]

The 720 showed up to a Market that wasn’t in any way prepared for it. Not enough Queen Airs came off the production line.

To the Duke question:

You could strap a 720 or a P&W 1340 to the B-60 wing an still have to spin it 2900 for takeoff. The Duke has a very small diameter  props(74in like a vintage Mooney), where as the C421 has 90in propellers. Diameter is everything when it comes time to takeoff, lack of diameter with a more aggressive blade angle makes speed in cruise which is one reason the Duke will Wax a Golden Eagle

Now strapping the 720 or one of the 600hp Trace V8’s on a Duke would be really cool, the Landing gear STC would be a nightmare with the FAA.

One would have to get some of those short Pitot tube tires that these youngsters have these days on the big 4x4 that never go off road.

 

[LTHTX]

N201MKTurbo,

I've seen you mention Joe Henderson a couple of times. How did you know him?

[N201MKTurbo]

10 hours ago, LTHTX said:

N201MKTurbo,

I've seen you mention Joe Henderson a couple of times. How did you know him?

I knew him pretty well, I used to fix the electrical systems on his air tractors. He was always blowing out light relays, the lights would stop retracting, the voltage regulators would fry. I fixed them all. In exchange he gave me keys to his shop and I could use his hangar and parts to work on my Mooney any time I wanted. I used to keep detailed lists of the parts I used from his parts room. I would give him the list and ask how much I owed him. He always crumbled up the list and threw it away and said don’t worry about it.

One time I was working on my fuel system and was draining my tanks into his underground tank. I was kind of soaked in gas, he comes over with a book of matches and is making like he is going to strike one and asks “can you see ok down there” kind of bizarre all things considered. There was about five years that I hung around SanTan Dusters. I didn’t see him much after the airport kicked him out. The last time I saw him was at a fireworks display in Gilbert a few months before the crash.

Edited July 11, 2021 by N201MKTurbo

[1964-M20E]

On 5/7/2021 at 6:55 PM, GeeBee said:

I thought a review of the sales brochure might be in order. I've had this since I was 11. The Golden Age.

 

scan the ad and post it as a PDF would be interesting to read

[GeeBee]

I will do that in the near future!

 

[M20F]

On 4/26/2021 at 12:56 PM, aviatoreb said:

I remember I once found an article by a guy who turbo-normalized his IO720 on his Comanche 400.  He was claiming he was getting 260 TAS at 25,000.  I can't find that article again.  It was quite a fun read.

 

Edit: I found it!  I remembered my numbers wrong - he was claiming 281mph TAS.  And he super charged not turbo normalized.

Butch Piper had a RayJay normalized 400.  It was up for sale a few years ago, no idea the performance numbers but I would expect impressive given Clarence’s 190 TAS NA.