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RPM/FF/Airspeed Numbers Review

Jcurry

Well Known Member
Hey Guys,
I have a 912 ULS. Would you please review my numbers below for RPM/MP/FF/Airspeed and see if they "jive" to you. My flight today was done at 2200 MSL, 90 degree F, no wheel pants installed, take off weight 1200 lbs.
I appreciate all opinions/advice. Thank you.

Altitude RPM MP FF IAS TAS

SL 5300 Max 29.9 5.0 N/A N/A (What is your max static rpm?)

Climb 5350 29.0 6.0 75 knt VSI 800 fpm

2200 msl 5000 24.2 4.5 92 knt 104 knt

2200 msl 5100 24.4 4.7 95 knt 106 knt

2200 msl 5200 24.5 4.9 96 knt 108 knt

2200 msl 5300 24.9 5.0 98 knt 110 knt

2200 msl 5400 25.1 5.4 99 knt 112 knt

2200 msl 5500 25.4 5.5 100 knt 114 knt
 
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Assuming this altimeter setting, temp/dewpoint for today:
KTIX 211847Z 13006KT 7SM SCT041 34/23 A3006

Your density altitude was 5059' (we'll call it 5000').

On a return leg from Oshkosh last year (one of the few times I can remember havng the pants off), I had a long stretch of flight at 5000 DA: 113-115kt TAS, 4.8gph, 25-25.3" MP, 5450-5500rpm. That matches up really good with yours.. though the gph is much different.
2200 msl 5500 25.4 5.5 100 knt 114 knt

I have a flight with main wheelpants (no nosepant) ON.. 5000' DA, 5200 rpm, 3.8gph, 21" MP, 108-110kt.

I have a flight with ALL pants on (missing the nose leg fairing): 5000' DA, 5000 rpm, 20.7" MP, 3.5gph, 106-107 kt TAS.
 
Assuming this altimeter setting, temp/dewpoint for today:


Your density altitude was 5059' (we'll call it 5000').

Rob,
Thank you for your reply. Very much appreciated.

When I took off, I believe AWOS was reporting around 1900 DA.
On my fuel consumption, still working to get my "k" value dialed in. I timed my fuel consumption yesterday. Based on that, I believe I'm averaging 5 gph.
Static RPM is 5300. Wondering if I should drop down to 5200 or just leave it alone? It is hot and humid down here in Fla right now...
 
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I don’t have exact figures but typically see 112-115kt true at 5200-5250 at around 2000’. Recommended static rpm as I recall was about 4600rpm which is what I pitched it to.

Edit: I just checked my original PAP, and it recommended 4960-5020 static as per Joe’s post below. I should have said 4960 not 4600. (Lesson: don’t rely on memory to explain what you did 7 years ago). Later versions of the PAP gave a blade angle as the starting point for prop adjustment.
 
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I think your static rpm of 5300 is too high, I would set prop to 71.3 or 71.4...at VY 75 kts I'm getting about 5180-5200....my full throttle max rpm at 2000' is about 5750 which probably would be better at 5650...my pitch is 71.4...next Condition Insp. I may drop it to 71.3
 
On take off at full throttle, 1000 ASL, I would see 5130 - 5150 rpm, rolling on the ground. At climb out at Vy of 75 kts, I would see 5180- 5200 rpm.

I think my prop was very slightly under pitched.

My friend, Bob had a 2016 RV-12 build that was pitched at 71.4 and he'd consistently see 5150- 5180, very, very rarely 5200 rpm at Vy 75 kts.

He cruised consistently between 5200 to 5300 rpm as he felt it was the sweet spot for his motor and prop set up. DA would be about 4000 to 4500 flying at 1500 to 2000 AGL, usually 3000 ft Altitude indicated.

His plane was unpainted, with wheel pants on all corners. Pretty typical for him was 107 kt IAS, and 112- 114 TAS at 5250 rpm. His burn rate was pretty consistent at about 4.3 to 4.7 gph. 912 ULS motor with 300 hours Hobbs. We ran 91 octane Mogas, usually with 1 to 3% ethanol, usually Costco, here in Southern CA.

Some will say the wheel pants are worth 5 kts. Some, especially the older guys, will say, getting on the ground to remove the wheel pants to add air for tire pressure is getting harder.... especially getting up off the ground after filling them up, mostly the mains.
 
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