Is my plane slow?

[bkthomps]

Just want a sanity check since I've put about 8hours in the plane in the past few days.

I am showing about 130KT TAS @ 7000-9000FT, consistently yielding about 140kt GS, I just want to see what other FP 150hp RV's are getting (even the 6 or 9 as well as the 4 and 3)

Van's published numbers are a cruise of 164KTS at 8000FT- what am I doing wrong?


O-320-E2D (low compression, 150hp engine)
Fixed Pitch Wernke Prop
RV-4

Now there are a few areas of improvement on the plane such as a lower rear empennage fairing that needs to be installed (just an upper on there currently)

Wheel Pants/Gear Fairings are "tired" and probably need to be replaced/redone as well as the intersection fairings. Cowl has some fitment issues that need attention, but I just don't see how some of you guys, even with 45 more HP are getting 185-195TAS

[dsmith1055]

email sent.
Dwight

[bkthomps]

I am getting a lot of emails and not a lot of posts in here, let's keep the discussion in the thread so others can chime in

I am seeing 2500RPM on a static runup at sea level, the mag drop is about 75-100rpm on each mag

Any other possible culprits? The thing that really bugs me is that the dynon skyview is configured for my engine parameters (150hp, etc) and it says that I am making about "55%ROP" when at 9000FT, 20.1inMAP and 2400-2450RPM

Does that add up?

[southtarnation]

My tired engined, poorly rigged and barely fared 160hp fp -4 was at least 30knts faster with an overly aggressively pitched wood prop. With the cruise prop the difference is a lot more. I would start determining what your speed is compared to a chase plane or an independent gps... Im def no expert but thats my experience.... Oh yeah, that was with no nose cone either.

[bkthomps]

I am verifying the speed with the dynon skyview system, garmin 430W, and even foreflight....they all agree on the GS, so that tells me the rest of the calculations are in order, the only calculations that are off to me (or that I do not make sense of) is the ROP calculations the dynon is doing

indicated fuel flow is around 9.2gph leaned out at 2400-2450rpm

[WAM120RV]

Hi

If you are pulling 2500 static that prop is much too fine for cruise speed. As Humptbump said something in the region of 2100 is more like it for a cruise prop.

Deal with the fairings.... see what speedyou get then, then determine how much your prop needs re-pitching. You will give ip some climb perfomance but unless you go constant speed you cant have your cake and eat it!

Another thought..... make sure you are not flying on the back end of the drag curve...... I have seen a lot of pilots do this. Set your cruise RPM straigh and level then trim her down just a bit. Yes initially she will descend but as the speed build you get more lif from the wings and she will come back to straight and level. keep doing this till you get to to point where the extra speed does not creat enough lift to stop the descent.

I am able to tease about an extra 10 knots out of my 9 by ding this.

[Sid Lambert]

It is slow if your numbers are correct.

At 8000 DA and 7.8 GPH I get 157 kts TAS.
At 2600 engine RPM and 8.6 GPH I get 164 kts TAS.

160 HP with a 79 pitch Sensenitch metal. James wheel pants with Vans cowl.

[bkthomps]

Originally Posted by humptybump

I would not make any assumption if you are basing your interpretations off of GS without flying the NTPS GPS track and using the spreadsheet - and then repeating it several times.

You will get a lot of valuable information performing two tasks:

1. fly multiple GPS tracks according to a standard procedure
2. use "search" here on VAF - you will get a log of great information

the skyview calculates TAS with the different sensors it has, other than my OAT being off (which i am open to) the rest of the sensors are calibrated dead on

[Ironflight]

Originally Posted by bkthomps

the skyview calculates TAS with the different sensors it has, other than my OAT being off (which i am open to) the rest of the sensors are calibrated dead on

Where is your OAT probe located, and does it appear to reflect reality (+/- a couple of degrees)? OAT can significantly affect the TAS calculations, so it needs to be very close to be of any use.

[Sid Lambert]

Ignore the EFIS. Fly the 3 or 4 heading test. Use the autopilot.