Prop and Performance RV-14

Don't want to create a new thread if one is out there but I'm at the point I need to order my prop. If there is a thread someone please let me know. I want to use a composite prop and with the aft CG issues and ramp appeal want to use a 3 blade. Easy enough I thought. Whirlwind was my first choice but they do not make one for the Lycoming 390 or Superior 400 and no the knew prop coming out is not good for anything over 200 hp. That leaves MT. Doing my due diligence and keeping with "Total Performance" it's difficult to find performance specs for this prop. One builder reports 171 knots (TAS) flat out with consistent 160-161 knots at cruise. This is not much data to make a decision on a MT prop. What I did hear earlier this week that Hartzell submitted there Raptor series 3 blade to Vans for performance evaluations for the 14. Suppose to be ready in May to give feed-back to Hartzell. Maybe someone at Vans could give input? If I wait till June-July to order my prop I'm cutting it close as I need to finish cowling after prop install. Want to be flying by Dec 2019, I hope.

Can't speak for the -14, but the MT has been a fabulous all around prop for my -7. Lead times can be long. Regarding fitting your cowlings without the prop, I had the same dilemma of having to wait for my prop delivery. I used the Flyboys cowlings alignment tool which you can rent or buy outright. Worked like a charm. I was able to complete my cowl fitting and installation sans prop. When my prop finally arrived, it fit like a glove.

Flat out at 171 is a bit slower that I would have expected. I can easily true 180 (verified several times via GPS triangulation) with my 2 blade composite Whirlwind and that is not 100% flat out effort. Fuel flow is quite unacceptable at that speed so it's not realistic for cruise unless you are late for dinner etc.

We get 171kts at 2450/ WOT 11 GPH, at 6000, 169, 10GPH At 8000.

Bob Bisbee

Agree with Nova RV

My data agrees with Nova RV. With an IO390 and the Hartzell blended prop as recommended by Vans you should get closer to 180KTAS. My normal flight pattern is to plan for 170KTAS at ~9GPH beginning of cruise edging up a few knots at end of cruise, this speed/fuel flow can be better at a higher cruise altitude. Because of some personal choices, I suspect mine is not the fastest -14. I’m a bit heavy with additional drag over the standard landing gear.

Most people claim a three blade will increase static performance and climb at the expense of about 5KTS in cruise. All the while running smoother.

Performance

Thanks, and appreciate the input. I'm not willing to give up 9 to 10 knots and hopefully more people can add to their performance numbers.

Be careful when comparing posted data.....
The entire picture needs to be known for each set of data to have an apples to apples comparison.

Marvin's posted data provides enough information (DA, RPM, MP, etc.) to do a good comparison to others if they provide all of the info as well.
Note that his RPM for all of the data points is max (2700) or nearly so.
I think most people do not fly in extended cruise flight at max RPM. More typical is 2400-2450. At this RPM range but the same conditions Marvin posted, an RV-14 typically cruises at 171-172 Kts (the 8000 ft DA cruise speed that is posted on the Van's web site HERE)

I have done extended cross country at DA altitudes of 10K - 11K and TAS speeds of 171 - 172 Kts in RV-14's with fuel burn at 8.2-8.4 GPH (no injector balancing effort done).

Agreed

rvbuilder2002 said:

Be careful when comparing posted data.....
The entire picture needs to be known for each set of data to have an apples to apples comparison.

Marvin's posted data provides enough information (DA, RPM, MP, etc.) to do a good comparison to others if they provide all of the info as well.
Note that his RPM for all of the data points is max (2700) or nearly so.
I think most people do not fly in extended cruise flight at max RPM. More typical is 2400-2450. At this RPM range but the same conditions Marvin posted, an RV-14 typically cruises at 171-172 Kts (the 8000 ft DA cruise speed that is posted on the Van's web site HERE)

I have done extended cross country at DA altitudes of 10K - 11K and TAS speeds of 171 - 172 Kts in RV-14's with fuel burn at 8.2-8.4 GPH (no injector balancing effort done).

Click to expand...

Agreed, What I posted was 75% power numbers because that was the OP’s question, maximum performance. I always cruise at 2400RPM and get closer to the numbers Scott references. I have tried many combinations I just like 2400RPM.

This quote is from Post #5. It is more inline with Scott’s concern that you carefully compare an appropriate flight condition when checking your performance. My preference is Density Altitude, DA.

”... My normal flight pattern is to plan for 170KTAS at ~9GPH beginning of cruise edging up a few knots at end of cruise, this speed/fuel flow can be better at a higher cruise altitude...”.

Marvin, would you mind sharing the rest of the spreadsheet? I'm curious about the RV-14A performance.

-14 numbers

gfb said:

Marvin, would you mind sharing the rest of the spreadsheet? I'm curious about the RV-14A performance.

Click to expand...

I will gladly share any data you want; however, I need to know what altitude your interested in and please understand almost all my data is for only 2400RPM (my 2700RPM data is only for finding the maximum nobody really flys there).

I will say the results are really well defined by Scott M. In post #7 above. Also, I record any data posted by Scott because it is the factory demo plane which I suspect is some of the best calibrated data out there.

Basically the -14 is fastest around 8 to 9000DA. Up to around 13,000DA you can save about 0.5GPH per 2000’. My information above 13,000DA has not been recorded often enough to get good averages.

Thanks Martin.
If you could share your numbers from 6k up that would be great. I'm suspecting the 14 is slightly more efficient than the 9?

-14 performance

gfb said:

Thanks Martin.
If you could share your numbers from 6k up that would be great. I'm suspecting the 14 is slightly more efficient than the 9?

Click to expand...

I suspect the 9 is a bit more efficient than the 14 due to weight, size, and higher aspect ratio. For the comparison your interested in I believe the best source is the Vans aircraft site under the performance tab or post #7 above.

There is a thread by JDA_BTR (might have been Bavafa) that may be a better match for your interest than my data. He did a search for performance by altitude and percent power which is very good for creating a standard POH. My interest was more of altitude and fuel flow because that is how I like to fly. I find an altitude that is comfortable then I consider wind, and then lean to a known fuel flow. For my aircraft that number revolves around 9.0GPH and about 8 to 9000DA unless comfort and wind pushes me elsewhere. If I want to fly faster I burn more if I want to stretch my range I climb higher or burn less. below is the outside envelope for my aircraft. Understand I am most likely slower than the factory demo because I built heavier and added drag with a larger landing gear.



This is the maximum envelope, I fly well inside this envelope. I find Rich of Peak operations abhorrently inefficient. At one time I was working on standard certified aircraft POH charts like speed at a percent power as a function of altitude then I realized that really is of no value to me.

A basic summary of how I normally fly would be 9000DA and above between 8.5 and 9.5GPH @ 165 to 175KTAS depending on weight and altitude. Those number are generally between Peak EGT and 25 Lean of Peak and around 63 to 68% power