A pressurized,.turbine Mooney?

[Yetti]

29 minutes ago, Pinecone said:

I don't know about these days, but a while ago, the serious aerobatic guys were running IO-360s to 3400 RPM for the extra power.

Along with high compression pistons and helicopter cams.

Engine life was NOT very long.

 

If you calculate the point at which the propeller tips go supersonic, the Mooney is already pretty close.    You don't want your tips supersonic.

[Pinecone]

Maybe they were running shorter props.  You do loose prop efficiency with the tips supersonic, but the big deal is the noise level goes up a LOT

[M20F]

There is T, S, I, and a host of other letters.  When you want to get serious about power on piston planes, that is when the letter G enters the conversation and your (W)allet leaves.  

[MikeOH]

1 hour ago, Yetti said:

Someone said it once already, you are not going to be a store enough Jet A in a Mooney to get you much past take off.  Possibly with a smaller turbine.

Isn't that the old LearJet joke?  After take-off, check in with departure and declare minimum fuel

[EricJ]

1 hour ago, Pinecone said:

Maybe they were running shorter props.  You do loose prop efficiency with the tips supersonic, but the big deal is the noise level goes up a LOT

Yes, they shorten the props.   The F1 guys do the same and spin the O-200s faster for more power and shorten the prop.

[Ibra]

8 hours ago, Yetti said:

Someone said it once already, you are not going to be a store enough Jet A in a Mooney to get you much past take off

Unless it’s JetA piston Mooney?

https://www.flyingmag.com/photo-gallery-photos-mooney-m10/

This could fit the bill if one is into JetA smell (from pistons) rather than JetA sound (from turbines), one just need to find the fetish bit they are after: JetA M10 have red leather and manual-automatic gearbox…not my type but I am sure someone will fall in love 

 

 

Edited October 30, 2024 by Ibra

[A64Pilot]

I don’t think Mooney’s props are anywhere near supersonic, because of ground clearance they are short to start with and do any of our motors turn more than 2700?

What is close to supersonic is the 1340’s on like a T-6 due to length and a C-185 on floats with a “Borer” as in long prop that is turning 2850 RPM

Warp drive propellors used to have an excellent tip speed calculator online, but I’m having trouble finding it, maybe someone with better search skills can?

[A64Pilot]

On 10/30/2024 at 9:24 AM, Pinecone said:

I don't know about these days, but a while ago, the serious aerobatic guys were running IO-360s to 3400 RPM for the extra power.

Along with high compression pistons and helicopter cams.

Engine life was NOT very long.

 

One thing that kills the aerobatic engines is the prop is a big gyroscope, and doing all that flipping around etc is hell on the crankshaft, the lighter the prop of course the less effect so the wooden MT’s are I think very popular, and an aerobatic prop does just the opposite pitch wise from oil pressure loss, they increase pitch where out props go flat, reason is imagine running wide open at High RPM, lose oil pressure for a sec and the prop go flat, RPM would get excessive, but if it increases pitch then it loads and slows engine and it’s safer. Turbine props do the same, they got to feather at loss of oil pressure.

In this video a Reno air racer loses oil pressure, prop goes flat, explodes, engine RPM goes to god know where and engine rapidly disassembles itself, listen to the audio, engine sounds like an air ratchet.

 

Edited November 3, 2024 by A64Pilot

[exM20K]

14 minutes ago, A64Pilot said:

I don’t think Mooney’s props are anywhere near supersonic, because of ground clearance they are short to start with and do any of our motors turn more than 2700?

What is close to supersonic is the 1340’s on like a T-6 due to length and a C-185 on floats with a “Borer” as in long prop that is turning 2850 RPM

Warp drive propellors used to have an excellent tip speed calculator online, but I’m having trouble finding it, maybe someone with better search skills can?

Should be pretty straightforward to calculate.

diameter (inches) * pi / 12 / 5280 * rpm * 60

even the big 210 prop tip is pretty far below speed of sound at SL.

The T6’s always brought conversation to a halt when i worked OSH.

[A64Pilot]

The R-1340 RPM red line is 2250, usual cruise 2000. I’m pretty sure the T-6 airshow planes are turning faster than 2250 just for the noise. How much I’m not sure but the old Thrushes ran the same motor and prop and while they were loud, they weren’t that loud.

[Fly Boomer]

3 hours ago, A64Pilot said:

Warp drive propellors used to have an excellent tip speed calculator online, but I’m having trouble finding it, maybe someone with better search skills can?

I'm too lazy to verify, but according to gegcalculators.com (never heard of them), the formula is:

                                          PI * Diameter (ft) * RPM
        Tip Speed (ft/s)  =  -----------------------------
                                                       60

The speed of sound is around 1100 ft/sec.

[A64Pilot]

The warp speed calculator also corrected for temp and maybe DA, I know temp changes Mach quite a bit but don’t know about DA. Seems like it would because the speed of sound in water is quite fast, I assume due to density? Speed of sound is variable and the warp speed calculator took that into account.

Anyway I think from memory our little airplane had a 108” prop and we turned it at 2200 RPM, that gave it a Mach number of about .9 and made it the loudest airplane we manufactured, for whatever reason Ag planes are exempt from noise regulations, but that airplane is also the only Ag plane that’s also Certified in the normal category, and it’s restricted to 2000 RPM then, but we increased the allowable torque limit so that the HP remained the same at 750 SHP.

Of course the Ag drivers aren’t stupid and understand that the higher torque is the gearbox limit and the gearbox doesn’t care about RPM, so they turn both the higher RPM AND the higher torque and get 825 SHP out of the 750 SHP certified engine  

Edited November 4, 2024 by A64Pilot

[A64Pilot]

Republic built a turboprop that the prop was supersonic, it was nicknamed the “Thunderscreech” do to its horrible sound level.

Scroll down to the section entitled noise, because if I told you, most wouldn’t believe me.

https://en.wikipedia.org/wiki/Republic_XF-84H_Thunderscreech

[MikeOH]

1 hour ago, A64Pilot said:

Republic built a turboprop that the prop was supersonic, it was nicknamed the “Thunderscreech” do to its horrible sound level.

Scroll down to the section entitled noise, because if I told you, most wouldn’t believe me.

https://en.wikipedia.org/wiki/Republic_XF-84H_Thunderscreech

Good read!

Best line, from one of the test pilots:

"You aren't big enough and there aren't enough of you to get me in that thing again"

[1980Mooney]

I liked these quotes:

• On the ground "run ups", the prototypes could reportedly be heard 25 miles (40 km) away.
• The shock wave was actually powerful enough to knock a man down; an unfortunate crew chief who was inside a nearby C-47 was severely incapacitated during a 30-minute ground run. 
• Coupled with the already considerable noise from the subsonic aspect of the propeller and the T40's dual turbine sections, the aircraft was notorious for inducing severe nausea and headaches among ground crews.
• In one report, a Republic engineer suffered a seizure after close range exposure to the shock waves emanating from a powered-up XF-84H.