The speed thing...How fast REALLY is plane...

[scottfromiowa]

O.K., I see a lot of Mooney drivers talking about their J's doing 160 knots on 9 gallons an hour.  Anyway, my 1966 M20E does NOT achieve this speed.  How do your planes do.  Really.  In real world.  What kind of cruise speeds do you see vs. fuel flow at altitude.  I completed a flight yesterday with a friend, golf clubs and 32 gallons of fuel on board.  We had flight following and winds were about as close to neutral as I ever see.  At 6500 feet leaned to 10GPH we had speeds of 135-154 knots with 146 coming up most frequently.  Return flight at 7500 feet 10GPH saw 130-145 knots.

I would say this is representative of my planes speed at 2500RPM and full throttle, i.e. 130-155 knots with an average of 140-145 knots showing on GPS.

What do you guys REALLY see as average GPS ground speed with your planes and at what fuel flow.  Do J's REALLY get 160 knots on 9GPH? 

Scott

[Parker_Woodruff]

My M20J would do 150-155 KTAS when LOP on 8.8-9 GPH. It would do 163-168 KTAS when ROP at about 10-11 GPH

[MARZ]

I see about the same as you Scott.   

9.5 - 10  gph

75 rich of peak

2450 - 2500  7500 - 8500 msl

ram air open throttle pushed all the way in and pulled back till the manifold pressure moves.

Course the best is on that long glide back down.....  well into the yellow then  

[scottfromiowa]

Thanks Jim.  Yesterday on return at 7500 feet I did my "big pull" on mixture and slightly enrichened to smooth.  Running about 10gph.  We were seeing 130 knots on ground speed so I enrichened mixture slightly (now indicating 11gph fuel flow).  Oil temp climbed as indicated on my digital EI indicator 20 degrees (one green indicator from red)...Cylinder temps also rose from 325-350 to 350-375...I leaned back to 9.5gph and got my peak indicator on EGT and enrichened back to 10gph.  Cylinder temps back down and oil temp back down...I saw NO increase in speed from the 130 knots with the enriching mixture at 7500 feet and the negatives of temperature.  Probably put me in the 50 degrees rich of peak triangle.  Winds abated and ground speeds increased to 140-145 knots about 1/2 way through return flight.

I can NOT get 6.5, 7 or 8PGH fuel flow at 2500 RPM.  I definitely can't get 155 knots on those fuel flows.  THAT IS pretty impressive speed...but as you don't have a fuel computer you are somewhat guessing on fuel flows in cruise, right?  Do you sump tanks to confirm after flights.  I sumpted mine for ten cross-country trips and the computer is within a gallon (probably the error is on my paint stick wet guess method.  Mooney's ARE impressive for speed, but in my E 2500 RPM full power and <25 +- peak yields a fuel flow in my plane of 10GPH and happiness in the engine.  I'm happy with a 145knot bird, but 10 knots in a J at same fuel flow would be marvelous.

[scottfromiowa]

Thanks Parker and Mike.  Parker did you fly mostly at 10GPH with the nice increase in speed?

[scottfromiowa]

I wish the G3 would come down in price for an upgrade.  The GEM (602) doesn't have numerical EGT readout only 25 degree bars...Would like the increased precision of the G3 and the slipperiness of a J (but not the expense).

[scottfromiowa]

Thanks Jim.  What RPM and manifold pressure and altitude for that fuel flow/result?  I would like to do a comparison with my E.

[rob]

For what it's worth, I have had a 430 in my M20C for about a year now. I checked the trip statistics last time I flew her, and it's currently showing an average groundspeed of 136 knots over 15,400 miles. That includes any time the plane is in motion, so climbout, patterns, etc.

In cruise, she'll do 148-152 kts while burning about 9.5gph.

[scottfromiowa]

Thanks Jim.  I'll give 2400 and 20MP a try at that fuel flow.  I'll report back on my speed.  Congrats Rob.  Your C is faster than my E at that fuel flow.

[sleepingsquirrel]

Regardless of what the airspeed indicator says, it is a well known fact that Mooneys are so fast that they often arrive ahead of the pilot. Present company excluded!

[rob]

Quote: JimR

 Very impressive, Rob.  Is she stock or modified? 

Jim

[Magnum]

My 205 makes exact book speed, that means 160KTAS at 65% HP at 7-8000 feet. I usually fly around 50dF ROP, that equals to 9.8-10 GPH.

It is really important to make sure all indications are correct. IMHO the shop won't bother if the ASI is 5 knots off at at 150KIAS. The same goes for RPM and MAP. When I bought my Mooney, the owner said she would make 140KTAS at 65% on a good day. The AIS was indicating more than 10 knots too low, and the MAP was reading almost 1" high. After changing the ASI and calibrating the MAP indicator the speeds were where they should be.

IMHO below 10GPH for a roundtrip (including takeoff and climb) and cruising at 160 KTAS is only possible when flying LOP for a long time.

[Shadrach]

Scott,

I do a lot of low alt (2000-3000msl) quick hops to Grandma's house in W. Maryland; for those trips I'm 30- 60LOP depending on DA.  I figure on ~150kts, but that's WOTLOPRAO making ~78% or better depending on DA. I'm usually alone (600-700 under gross). I am always 2500ish RPM when level at any alt.

I flight plan for 150kts during normal cruise (6500 to 9500msl is typical) as well.  At cruise altitudes, I run anywhere from 15LOP to Peak depending on CHTs.  Above 11K, I'm almost always 100ROP.  In a 4 way GPS run (3 mins at each heading) our calulations showed 145kts at a DA of nearly 16K (500 under gross). Certainly potential for error, but I doubt it to be more than 5kts.

In the mid-atlantic during winter,  we have cold (18-30df) high pressure days and can see DAs that are more than 1000ft below SL.  I can pull 28 inches at 2500 RPM down low with the ram air open. I've made quite a few trips to Grandmas with indicated airspeed in the bottom of the yellow arc (155kts). 

The truth is that people fly their planes differently, manage powe differently in addition to the ship to ship differences in rigging, build precision and MX. Our numbers are all over the place because of it.  

My very stock F model seemed to be nearly identicle in performance to my hangar neighbor's Comanche 250...even side by side in flight heading to fly-ins.  It turns out he pulls back to 25"X2500 at TPA on climbout because he was taught that back in 1978. I, on the other hand only really manage temps, I have a target set of temperatures and take all the power that I can within the personal limits I've set for the engine.     

[scottfromiowa]

Hi Ross.  Good stuff.  I don't fly that low usually.  You are definitely making more power there.  My plane hs laser windshield and cowl closure and flies ball centered in cruise.  Maybe I should ask for this:

At 6500 feet WOP...Ram Air open (if you have it) at 2500RPM and a fuel flow of 10GPH How fast is your plane?  I'm going to do three minute compass rose speed test.

I have noticed I lose about three knot/gain three knots by closing roof ram-air.  About 1-3 knots (gain) for closing cowl flaps.

I always flight plan for 10gallons of fuel (1 hour) AT Destination.

Any thoughts on what was happening with oil temp cylinder temp?  Anyone?

[Shadrach]

The last 4-way test we did that was close to what your asking was at 7K and completed in the late fall a few years back.  IIRC at WOT RAO 2500rpm and 100ROP the calculation was a hair over 154kts.  

I should probably see how it runs with the recently installed engine.  

[Shadrach]

WRT Short and low hops:  The DC/Balt Metro gives the Mooney more than a speed and navigation advantage. Traffic can slow you average speed in a car to 30MPH or less, and it's a crap shoot as to when and where it will be the worst some times. Faced with a 150ml RT that could take anywhere from 2:20min to 5:30 mins in a car, I'll take low, fast and direct for 15 to 20mins in the Mooney everytime...

[1964-M20E]

Scott

 

I jut flew 2.5 hours today. The first leg was 29nm at 2500’24”, 2500rpm ROP using the GEM 602, second leg 110nm 5500’ WOT and ram air about 24”, 2500rpm ROP and the third leg 113nm 7500’ about 22” WOT and ram air ROP.  I averaged 135 to 144kts GS on the GPS and I put 23.4 gallons in the plane when I returned home to NEW.  Winds were calm this morning.  So just under 10GPH average with a stock E model no mods.

[Shadrach]

If you were ranging from 135 to 144 on the GPS, then winds were not calm, or you were riding down and climbing up thermals... GS range at verying headings and altitudes is not much of a data point... Also, if you were pulling 24" at 2500ft and 24" at 5000ft then I imagine you were flying part throttle? If those are in fact your real world numbers then I know of a stock F that would walk away from your plane. No big difference in terms of block times, but it indicates something might be amiss with your E...

[Becca]

So, fastest I've ever gone in my 201 was the Lone Star Air Rally - results here (for proof): http://www.sportairrace.org/id405.html, 160 kts (184 mph), and I was WOT and full rich for cooling, so burning a ridiculous 18 gph.

I think we typically cruise closer to 145 kts and 9.5 gph LOP.

[jetdriven]

We have put 100 hours on our plane so far and it depends on altitude, but generally between 3000-5000 in cruise it is WOTLOP 2500 RPM and 50-100 LOP.  5000'-7000' it is WOTLOP 20-50 LOP 2500 RPM.  Above 7000 we run WOT near peak and all of these net you 152-154 KTAS and 9 GPH (low) to 8 GPH (high).  We recently trimmed it better so maybe 2 more KTAS there.  Running at 2400 RPM costs you 1.5-2 knots, but lowers fuel flow .2 to .3 GPH and MUCH lower noise.  This all nets around 17 NMPG. Flying slow say 110 KTAS and 6 GPH nets you around 10-15% more NMPG but with a 24$ an hour dry cost it is largely offset.   

Our machine is a 1977 J model, 5000 AFTT, 1400 SMOH, McCauley 2 blade prop, stock antenna set, nose gear doors need rerigged, paint is 15 years old, and no ram air. I think there is 3 more KTAS hiding between gear door rigging, flap and aileron rigging, eliminating the ADF antenna, and some nonstandard fasteners. so the 9-9.5 GPH 155 KTAS early J's are mostly correct.  I think the later MSE's etc are 5 KTAS faster.

[1964-M20E]

So I like Disney World.  :-))) I'm sure up and down has a lot to do with it. 

The two long legs were 005 degrees and 175 degrees.  I did not write the speeds down just some of the numbers I saw when I looked.

at 2500' yes thottled back  5500' was WOT and best I can remember 24" @ 2500. 

I've always thought mine was a slower E model but I've only flown P and Cs before and the paint is probably is steeling 5kts from me.

 

[docket]

At 17 GPH, 2550 RPM and 23.1 on the manifold my S will show 183 kts TAS all day long at 9000 ft with 75 gallons on board and just myself.  At 18.6 GPH, 2700 RPM and 24 on the manifold the plane will show about 186 kts TAS at the same altitude and conditions.  It won't run LOP worth a damn although i have not put in GAMI's.  

[scottfromiowa]

I can NOT get 8GPH fuel flow up high with WOT and 2500RPM.  My engine will run rough before I get there.  At 7500 feet yesterday with big pull & then just enrichening to smooth I'm above 8GPH....HMMMMmmm.  I have to enrichen to find peak so know I'm LOP, but my fuel flow is NOT that low.  I might get 9GPH, but NOT 8.  Everyone can get 8GPH fuel flow at this altitude with WOT?

[jetdriven]

We can get 8.0 GPH st 2500 RPM at 7500' but it is quite lean at that setting, maybe 50-75 LOP.  We use more like 8.5-8.7 GPH. Are you at WOT?  The air distribution is more even there.  Try soaking your injectors in Hoppes #9 or acetone overnight and clean them up.  What is your GAMI spread?

[scottfromiowa]

Quote: Shadrach

The last 4-way test we did that was close to what your asking was at 7K and completed in the late fall a few years back.  IIRC at WOT RAO 2500rpm and 100ROP the calculation was a hair over 154kts.  

I should probably see how it runs with the recently installed engine.