Performance: RV-7, IO-360, CS.

G'day folks,

My search did not find a suitable thread, so this new thread provides those interested with cruise performance for our RV-7.

RV-7, #72450, tip-up, Aerosport IO-360 M-1B, E/Pmag combo, Hartzell BA F7496-2 CS prop, manual trim, built to plans, Dynon D100 EFIS/D120 EMS, Lowrance 2000c GPS. Finished & painted basic weight 492kg (1085lb), CofG 1987mm (78.24 inches) empty.
TTIS for all data was about 28 hours.

The following data all observed from the EFIS/EMS/GPS 'out of the box' - no calibration corrections. Observed density altitude about 7700 ft. AUW 635 to 680kg (1400 to 1500 lb), mid CofG.

Notes:
Due elec ignition: max normal RPM 2600.
Max MAP is 22 inches below 2350 RPM.
Mixture leaned to peak, and indicated power in %, as observed on EMS for all data.
Suspected pitot/static error of about minus 4KTAS from GPS box.

Full throttle/2600RPM/84%/38 litres(10 USgal)hr/149KIAS/166KTAS.
Full throttle/2500RPM/81%/36.5 litres (9.6 USgal)hr/148KIAS/166KIAS.
Full throttle/2400RPM/77%/35.5 litres (9.4 USgal)hr/145KIAS/163KTAS.

21.5" MAP/2300RPM/66%/30 litres (7.9 USgal)hr/132KIAS/148KTAS.
21.5" MAP/2200RPM/63%/29 litres (7.7 USgal)hr/132KIAS/148KTAS.
21.5" MAP/2100RPM/62%/28.5 litres (7.5 USgal)hr/129KIAS/145KTAS.
21.5" MAP/2000RPM/61%/27.5 litres (7.3 USgal)hr/127KIAS/143KTAS.
21.5" MAP/1900RPM/58%/26.5 litres (7 USgal)hr/125KIAS/141KTAS.
21.5" MAP/1800RPM/54%/25 litres (6.6 USgal)hr/120KIAS/135KTAS.

From other data, I estimate that, if wheel fairings only are removed (leg & upper intersection fairings still fitted), we would have to reduce planned cruise TAS by 7% for the same planned (observed) fuel flow.

Regards,

Bob

Interesting figures. I have basically the same setup but using a superior IO360 with horizontial induction, 2 slick mags.Rv7 with the same prop. At 8000 and 65% power I normally average 165 knots ground speed at 30 Ltrs/hr.
For flight planning I work on 155 knots down low 165 if I can get up to 8000 or so.

Peter

Thanks for the datapoints guys. I wonder what the differences are in configuration that allows Vans to get 174KTAS at 75% on 180hp, 8000'. 8Kts/9mph seems like a significant difference.

http://www.vansaircraft.com/public/rv-7per.htm

0-320 with the same performance

My 6a (1125 lbs)160HP CS gets 162-163 knots at the same configuration of Full throttle/2400RPM/ based on gps ground speed calculations from different directions and averaging the numbers
Wonder what the other 0-320's are getting?

grayforge said:

Thanks for the datapoints guys. I wonder what the differences are in configuration that allows Vans to get 174KTAS at 75% on 180hp, 8000'. 8Kts/9mph seems like a significant difference.

http://www.vansaircraft.com/public/rv-7per.htm

Click to expand...

I can easily get 174KTAS @ 8000ft with my O-360 w/carb cranking ~2650 rpm. I do however burn a little over 10gph at that speed because if I lean it to best power and 2700rpm, the oil temp starts to climb over 200°F and the CHTs get up above 380°F in my bird.

I have an 85" FP Sensenich metal prop.

At 75% power 8000 feet I get 175 knots so I guess that's as per vans figures. I find 65 % and 165 knots gives a better fuel consumption.

Peter

9500-12500 is a sweet spot for mine.

Last Saturday coming home I was WOT, 20.7"mp, 8.4gph, 2450rpm doing 178-180kTAS. I hardly ever throttle back below that...as my Bonanza friend told me....I didn't get a fast plane to fly it slow.

At 6600'DA, WOT, 2600rpm leaned to best power is 189kts TAS.... Fuel burn is ~13gph.

Your numbers seems slow, perhaps much slower than the 4k you are suspecting. I would first get my pitot/static check and possibly calibrated to make sure I am getting the correct speed. Then look else where as you ought to get a better speed with those settings.

In my 7A, I get 163-5KTS at 22" and 2350 @8000' and my burn rate is about 8.5
As for ground speed, yesterday was around 140K with the same setting

THANKS

Thank you all for the feedback.

I will investigate further as we build time on the aircraft.

We have just replaced the continuous duty solenoid on the firewall (as supplied in the kit). The solenoid was leaking about 0.25 volts per day, and I was recharging the battery (Odyssey 680) frequently to gain enough grunt to start the engine.

Degradation in battery performance was gradual until, eventually, the battery would gain the volts, but not enough current to turn the prop. Volt/amp readings after start were normal/logical. Finally, the visible and continuous drop in battery voltage after switch on and before start indicated the problem, and cause was isolated to the solenoid. Now it is 5 weeks since the solenoid was changed and we last flew. Since then the battery has held voltage at least. Weather permitting, we will fly tomorrow and again check both battery and cruise performance

Regards,

The following data all observed from the EFIS/EMS/GPS 'out of the box' - no calibration corrections. Observed density altitude about 7700 ft. AUW 635 to 680kg (1400 to 1500 lb), mid CofG.

Notes:
Due elec ignition: max normal RPM 2600.
Max MAP is 22 inches below 2350 RPM.
Mixture leaned to peak, and indicated power in %, as observed on EMS for all data.
Suspected pitot/static error of about minus 4KTAS from GPS box.

Full throttle/2600RPM/84%/38 litres(10 USgal)hr/149KIAS/166KTAS.
Full throttle/2500RPM/81%/36.5 litres (9.6 USgal)hr/148KIAS/166KIAS.
Full throttle/2400RPM/77%/35.5 litres (9.4 USgal)hr/145KIAS/163KTAS.

21.5" MAP/2300RPM/66%/30 litres (7.9 USgal)hr/132KIAS/148KTAS.
21.5" MAP/2200RPM/63%/29 litres (7.7 USgal)hr/132KIAS/148KTAS.
21.5" MAP/2100RPM/62%/28.5 litres (7.5 USgal)hr/129KIAS/145KTAS.
21.5" MAP/2000RPM/61%/27.5 litres (7.3 USgal)hr/127KIAS/143KTAS.
21.5" MAP/1900RPM/58%/26.5 litres (7 USgal)hr/125KIAS/141KTAS.
21.5" MAP/1800RPM/54%/25 litres (6.6 USgal)hr/120KIAS/135KTAS.

Click to expand...

Gooday Bob,

First of all get your static corrected, otherwise the numbers may or may not be worth much to you. It seems like you did these all at 7700DA, however the % power you have achieved at that height with 2600 RPM is somewhat at odds with reality.

I think I know how you have seen these numbers, either the EMS is not programmed right, or you have some how tricked the engine monitor to think you were at or just past peak get and that being so with the fuel flow you had, the calculated HP is going to be as you have shown. 84% power at that DA, if you were doing that she would have been going way faster

Peak EGT is not the place to be doing performance comparisons as it is not best power (more like75-80 ROP) and say 10-20 LOP for economical comparisons, when at these altitudes.

Also why is your Max/normal RPM 2600 ? The engine should be good for 2700.

Check your PM's, and give me a call.

Best Regards

David

The Same

I'm with Brian on this one. My stats are almost exact. Above 5000 I'm running WOT and leaned. My Whirlwind 200 RV prop has a sweet spot of 2450RPM.

I always try to got as high as possible based on Winds Aloft.

Fast and efficient is nice. So is passing Bonanza's and Mooney's.

hydroguy2 said:

9500-12500 is a sweet spot for mine.

Last Saturday coming home I was WOT, 20.7"mp, 8.4gph, 2450rpm doing 178-180kTAS. I hardly ever throttle back below that...as my Bonanza friend told me....I didn't get a fast plane to fly it slow.

At 6600'DA, WOT, 2600rpm leaned to best power is 189kts TAS.... Fuel burn is ~13gph.

Click to expand...

Clocks Slow, Plane Fast

G'day again,

and thanks again for the comments.

I flew yesterday in company with an RV-8A (same engine, MT 3 blade CS) - both aircraft full fuel, I was solo, he was two up. QNH 1025, +14 deg C @ MSL. At 5K DA 24/2400 leaned to peak, my ASI reads 140KIAS and the RV-8A reads 150KIAS. Quite a bit more position error than the 4KT determined during my GPS box, and that error would give me cruise performance close to that claimed by Vans. Our altitude readings were within 100ft. The RV-8A was checked against a Bonanza, so should be close, but I have yet to gather the position error data for either aircraft.

I flew the previous GPS box in summer with the associated turbulence, so a re-fly in smooth air will happen between fun events.

For David Brown:

Thanks for the hints. I chose to lean to peak because that was a quick way to repeat a similar mixture setting for each data point. I was gathering 'observed' data, which is repeatable and usable for my aircraft, though not for any other aircraft. This data set was not to determine cruise performance. I recorded it as a quick look to guide further testing.

I would have preferred to gather all the data above full throttle height of 22 " & so remove the discontinuity once I reduced prop below 2350 RPM (max MAP due elec ignition), but 7500ft was max available due controlled airspace. So I kept below that, and then realised I would have to reduce throttle (MAP) below 22" when below 2350RPM. My transponder was on, but had not then been ticked for AD/RAD/47, and I did not want to inconvenience IFR traffic.

Elec ignition also means reduce from 2700RPM to 2600 RPM as soon as safe to do so with my Hartzell BA prop.

I am aware of your opinion on leaning, and I am sympathetic, but will hasten slowly once I am more familiar with air-cooled flat fours, mine in particular.

Initially I was keen to complete a full flight test program of the performance, using calibrated data, but realised I am over it. I hope I have sufficient good days left in my life give priority to family, friends, good ale and fun flying. Gathering performance data will happen as a by product of other flying priorities. Currently I have sufficient handling and observed performance data to operate our aircraft safely and conservatively, if not completely accurately. But it is repeatable, and my envelope will expand as the data is analysed and included in the POH.

I will be at Narromine. Unfortunately we will have to leave either Friday evening or early Saturday morning, so probably a face-to-face yarn will have to wait. I expect that you will be very busy. Good luck, and please pass my regards to 'Blemish'.

Duly noted. If you are there on the Friday, while busy, it is always good to catch up with mates mates. Blem will be there.

Bob, in my opinion, simply fix your static error, that way altimitry errors are going to be within spec, TAS and any wind vectors are true, and then just enjoy your machine.

Cheers

DB.......the other DB