Cruise Speed for a Mooney Screaming Eagle (280 HP)

[M20S Driver]

I'd say your numbers are close to mine although you will want to try the Pixie hole for your baffles which helped me. Also your T/O fuel flow is to low. I can get close to 400 degrees initially on the Factory guage but immediately take action to reduce the temps. Also I find the Moritz gauges read higher than the G2 engine monitor. This,is particularly true on the EGT'S. if I belived the factory gauge the heads would have melted by now. This is the long way of saying get an engine monitor before you get overly concerned on the temps you describe. Of course if you have a engine monitor that is a differant story.

 

My CHT#2 as measured by the Moritz is 50 deg C higher than JPI's measured numbers. My hottest cylinder is also 50 deg hotter than the cylinder #2 CHT.  This gives me a built in safety factor for my CHT's since it is reporting the CHT for the hottest cylinder.  I only use the Moritz numbers for take-off since it is easy to look at.

[aviatoreb]

They did a good job for me. Another option that many use is Weber Aircraft an MSC in Lancaster Pa. I've used them also for both sales and service. They do an extensive air check as I understand it. Make a call to both.

 

Thanks.  Huh - following up with an air check certainly sounds more attractive than just a ground check for rigging.

[Cris]

The factory EGT is located below the union of all three cylinder exhaust pipes in the common section going to the muffler. The engine monitor probes are located close to the exhaust of each individual cylinder. These engine probes only see the exhaust gas from it's cylinder and then get a chance to cool until it is their turn again in the cycle. The OEM gauge gets exhaust from all three cylinders on its side and sees the exhaust heat three times as long, only waiting for the exhaust cycle from the other three on the opposite side of the engine. The OEM EGT gauge is always going to report a high temp reading because of this extra long exposure to the exhaust gas.

 

The OEM CHT is located on the #2 cylinder. It only reports what is happening with that cylinder the other five are unknown. It is a common problem with these planes to have this #5 CHT run anywhere from 40°F to as high as 100°F more than the #2 CHT (especially in the climb after take-off)

Tom That is a great explanation on why the temps read high on these models. Thanks

[harrispa]

I find that my Eagle meets or exceeds the POH numbers and I am very pleased with it. Below are professional evaluations for the M20R/S airframe with different props showing cloes to POH numbers. The airframes and engines are virtually identical so the cruise should be very close to the same for a given RPM. The only variable that makes a difference is the prop.

http://www.mooneypilots.com/mapalog/2005_M20R/2005_M20R.htm

http://www.mooneypilots.com/mapalog/M20S_evaluation/M20S_eval.html

http://www.mooneypilots.com/mapalog/M20R%20Evaluation/M20R.htm

[wrench]

Our a&p here at Zeeland finds that on many Mooneys he maintains the main gear doors dont close up tightly. Typically 3 to 5 knot gain when they are adjusted for proper closing. I can't confirm this personally but it is just another area for your mechanic to look at if you think you are losing speed. Good time to check is at annual when they do the gear swings.

Bill

[M20S Driver]

That is interesting. I was suspecting that since I seemed to have lost 3-4 knots since the last annual. I am looking into mounting a camera behind the wheel wells on the fuselage to check that. The annual is 3 months away and we will definitely check that again.

I sometimes get a slight right turning tendency which I can not explain. It may be the gear or a slight fuel tank imbalance.

[M20S Driver]

Zane,

 

8000 to 10000 feet full throttle, 50-70 deg rich of peak gives me 178-180 knots.  I will try the richer mixture that you mentioned (125 deg  ROP) just to find out what the performance is.  Most of my flights are short (1-2 hours) so I can l can live with 10 knots less and have a happier engine and fuel tank

 

Masoud

I tried the full throttle and 100-125 deg f rich of peak last weekend at 3100 lb take off  weight cruising at 6500 feet.  I got 184 knots at 18.5 gal/hour versus 179 knots at 16.5 gal/per hour (50 deg rich of peak).  I gained 5 knots but burnt 2 gallons more fuel per hour.  My conclusion is that at 177-180 knots, the engine, the airframe, and my pocket book are happier in a long body Mooney with 280 HP engine.

 

Masoud

[Cruiser]

just came in from a flight this afternoon, 9000' WOT (20.5) x 2350, 5°F LOP and 12.5 gph gave me 171 KTAS.

The EDM 830 calculated 59% HP (310 HP conversion) and TKS

[M20S Driver]

just came in from a flight this afternoon, 9000' WOT (20.5) x 2350, 5°F LOP and 12.5 gph gave me 171 KTAS.

The EDM 830 calculated 59% HP (310 HP conversion) and TKS

Is that 5 deg LOP or 50 Deg LOP?  My engine runs rough after 20-30 deg LOP!

[Cruiser]

5 deg LOP no need to go any more than that at 9000'

the 12.5 gph might be a little high. it is right between the higher OEM FF reading and the lower Shadin FF readings. I think the Shadin is correct.

[M20S Driver]

5 deg LOP no need to go any more than that at 9000'

the 12.5 gph might be a little high. it is right between the higher OEM FF reading and the lower Shadin FF readings. I think the Shadin is correct.

Hi Cruiser,

 

I looked into flying LOP and the POH only gives the guidance to fly it at 50 deg F rich or lean of peak.  I called Mooney in March and they told me that they no longer recommend LOP but is a certified option.  I also read that if the power is less than 65%, you can run at peak EGT but again Mooney did not recommend that.  The LOP concept does make sense but I was not able to find any documented guidance on it. I know Savvy raves about the LOP with GAMI's.

 

Masoud

[carusoam]

The IO550 loves LOP. The POH outlines how to do it.

MooneySpace discusses it in adnausium.

APS gives us the red box to follow, Or avoid.

Check your FF vs peak EGT of each cylinder to determine the ? spread.

At low altitudes, the 550 can go 100dF LOP before it just shuts off.

Not all Mooneys got a JPI or Gem, but they should now.

Flying a few degrees past peak, burns all the fuel and maintains most of the available power.

The nice curvy intake tubes with balanced injectors is all it takes...

To increase efficiency use lower rpm settings and 50df LOP. The cost will be at least 10kias...

Did I miss anything?

Best regards,

-a-

It's dissapointing to hear the factory not recommending LOP. But then again, there are engine experts that we can see for a less biased set of rules to follow. Look up APS to find out about their instrumented engine analysis studies. Fortunately the IO-550 is a popular engine and has seen a lot of studies.

The factory has a way of promoting how fast their planes go. LOP isn't it. A non sensible approach to LOP can ruin cylinders, and a nonsensible pilot will be dissapointed with the factory.

[M20S Driver]

Checked my GAMI spread and it was .5 gallons on my 280 HP Screaming Eagle. Ran 20 deg LOP at 5500 feet and 65% power. CHT dropped 22 degrees and fuel flow dropped by 1.5 gal. Not bad for cross country flights

I flew WOT at 8500 feet and 120 deg ROP at 3100 lbs and was getting 185 knots compared to 180 knots at 50 deg ROP. It is not worth the couple of extra gallons to get 5 knots.

The IO550 loves LOP. The POH outlines how to do it.

MooneySpace discusses it in adnausium.

APS gives us the red box to follow, Or avoid.

Check your FF vs peak EGT of each cylinder to determine the ? spread.

At low altitudes, the 550 can go 100dF LOP before it just shuts off.

Not all Mooneys got a JPI or Gem, but they should now.

Flying a few degrees past peak, burns all the fuel and maintains most of the available power.

The nice curvy intake tubes with balanced injectors is all it takes...

To increase efficiency use lower rpm settings and 50df LOP. The cost will be at least 10kias...

Did I miss anything?

Best regards,

-a-

It's dissapointing to hear the factory not recommending LOP. But then again, there are engine experts that we can see for a less biased set of rules to follow. Look up APS to find out about their instrumented engine analysis studies. Fortunately the IO-550 is a popular engine and has seen a lot of studies.

The factory has a way of promoting how fast their planes go. LOP isn't it. A non sensible approach to LOP can ruin cylinders, and a nonsensible pilot will be dissapointed with the factory.

[Danb]

I would not hesitate to have your plane rigged at Weber Mooney Svc Ctr..ask for Dorn..he's

Very good and it is an honest shop at K lns. LAncaster pa

[M20S Driver]

I'd say your numbers are close to mine although you will want to try the Pixie hole for your baffles which helped me. Also your T/O fuel flow is to low. I can get close to 400 degrees initially on the Factory guage but immediately take action to reduce the temps. Also I find the Moritz gauges read higher than the G2 engine monitor. This,is particularly true on the EGT'S. if I belived the factory gauge the heads would have melted by now. This is the long way of saying get an engine monitor before you get overly concerned on the temps you describe. Of course if you have a engine monitor that is a differant story.

Hi Cris,

Is there any time limit on how long to run at 2700 rpm and WOT at sea level take off on your screaming eagle STC? My STC is for 280 HP and doesn't specify anything. I usually pull the power back to 24 inches at CHT of 380 and speed it up to 120+ knots. This is usually at about 2 minutes into the flight.

Thanks,

Masoud

[Cris]

Masoud. If you go to www.deltaaviationllc you can download the STC flight manual supplement for the Ovation 3 which is the 310 hp. Within that manual there is no time restriction per say except pg 8 descriptive engine data. It states max continuous power is 310 bhp/2700 rpm & max recommended cruise power is 262 bhp/2550 rpm.

[M20S Driver]

Hi Cris,

I checked out the STC for the 310 HP on delta aviation's web and it is more complete than the STC on my plane. There is no Max recommended cruise power percentage on my STC document but it uses the same tables as Ovation-1. I calculated my max cruise HP to be around 240 HP at 2500 rpm at around 17GPH (50 ROP). There is no time limit specified on either one of the STCs for continuous max power operation.

Masoud

[M20S Driver]

Update. Replaced the sagging engine mounts and gained 3 or 4 knots in cruise speed. With a slight left rudder, I got 187 knots at 7500 feet with WOT AND 80 deg ROP. The plane was at 3200 lb and OAT was at 18 deg C.

Masoud

[co2bruce]

Our standard Eagle cruises at 178-180 all day.

[M20S Driver]

What is your fuel flow at that speed?  My 280 HP Eagle burns 17.5 GPH at 85-100 ROP.  

[philiplane]

Cruise speed is impacted more by CG variations than by rigging or tiny engine tweaks. One reason two blade props are faster than three is that they are lighter, resulting in a slight aft shift of CG compared to a three blade. Add a lot of panel goodies with a three blade prop and you make the forward CG problem worse. 

 

You can vary the cruise speed over a 3-10 knot range on most planes just by shifting the CG. Carrying extra weight in the aft baggage is normally required to get book speeds from a plane with full fuel and only front seat occupants. You may need 40-60 pounds there to help, depending on how much weight is in the front seats.

[Robert C.]

What is your fuel flow at that speed? My 280 HP Eagle burns 17.5 GPH at 85-100 ROP.

Many variables, Philip mentioned CG.

The other obvious ones are altitude, mixture and prop settings. My Ovation with the same engine will run those speeds and better 50 LOP with 13.6 Gpgh at 9000ft, WOT, 2450rpm.

So get an engine monitor and start flying LOP