B

bkthomps

Well Known Member
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
 
Last edited:
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?
 
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.:eek:
 
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
 
Prop too fine

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.
 
Last edited:
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.
 
humptybump said:
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
Click to expand...

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
 
bkthomps said:
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
Click to expand...

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.
 
Ironflight said:
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.
Click to expand...

in the NACA duct, which I am now seeing has plenty of controversy associated with it
 
Yes but the Skyview cannot calculate or account for Static Position error (Ps - error due change in local static pressure as AOA changes). The NTPS GPS test will allow you to calculate your Ps (static error) throughout your airspeed range and apply this value to your IAS to obtain CAS.

OAT errors can be signficant depending upon probe location which also results in a corresponding TAS error. If you give Skyview garbage it will calculate garbage.
 
OK, with the OAT in the NACA duct, do like others are saying - ignore the EFIS and go back to old-fashioned data collection. Use one of the NTPS calculators and GPS to figure out your airspeed calibration, use accurate altitudes and airspeeds, and figure out how fast (or slow) you are really going). You will probably find that you are a little slower than you'd like due to the fairing issues you described, but not as slow as you think. Under propped? Probably. You are going to find that your "slowness" is due to a little here, a little there, some instrumentation, etc. Find five knots each in four places and you have twenty knots!

Paul
 
Just to repeat others, there is something wrong with your TAS calculation. Your first post said 130 KTAS and a consistent 140 knots ground speed. No one is so lucky that they always have a 10 kt tailwind!
 
Here are all of the RV race speeds with a 320 engine

Reference www.sportairrace.org Records and Stats.

Race Record (RR) # - Race - Date - Class - Aircraft Type - Pilot - Speed Kts - Speed MPH
225 AirVenture Cup 2008 7/27/08 RV Red RV-4 Murphy, Chris 186.01 214.06
138 Texoma 100, 2008 4/20/08 RV Red RV-4 Murphy, Chris 183.67 211.40
65 AirVenture Cup 2007 7/23/07 RV Red RV-4 Murphy, Chris 180.33 207.52
228 AirVenture Cup 2008 7/27/08 RV Red RV-3 Vasey, Bob 179.96 207.10
466 TVA II 2009 10/18/09 RV Red RV-4 Benton, Cam 179.23 206.25
67 AirVenture Cup 2007 7/23/07 RV Red RV-6A Klusmier, Larry 178.90 205.87
1076 Thunderbird 150 10/8/11 RV Red RV-7 Baker, Seth 178.53 205.45
258 Grace Flight 2008 10/5/08 RV Red RV-4 Murphy, Chris 178.51 205.43
789 Rocket 100, 2010 11/20/10 RV Red RV-7 Baker, Seth 178.47 205.38
70 AirVenture Cup 2007 7/23/07 RV Red RV-3 Vasey, Bob 178.15 205.01
315 Taylor 100 2009 3/16/09 RV Red RV-4 Benton, Cam 178.02 204.86
790 Rocket 100, 2010 11/20/10 RV Red RV-8 Jones, Bryan 177.27 204.00
72 AirVenture Cup 2007 7/23/07 RV Red RV-6 Weisgerber, David 177.92 203.91
468 TVA II 2009 10/18/09 RV Red RV-4 Murphy, Chris 176.54 203.16
1152 Rocket 100, 2011 11/19/11 RV Red RV-7 Baker, Seth 175.78 202.28
1509 Thunderbird Air Race, 2012 10/13/12 RV Red RV-7 Baker, Seth 175.60 202.08
303 Rocket 100 2008 11/23/08 RV Red RV-4 Murphy, Chris 174.92 201.30
541 West Texas 100 6/6/10 RV Red RV-4 Benton, Cam 174.17 200.43
121 Rocket 100, 2007 11/18/07 RV Red RV-4 Benton, Cam 174.12 200.37
500 Taylor 150 4/11/10 RV Red RV-4 Benton, Cam 174.11 200.36
1293 GNAR III, Ephrata, WA 6/16/12 RV Red RV-4 Ford, George 173.91 200.13
726 Grace Flight 2010 10/2/10 RV Red RV-4 Benton, Cam 173.76 199.95
699 Pagosa Springs 2010 9/26/10 RV Red RV-4 Benton, Cam 173.65 199.70
646 AirVenture Cup 2010 7/26/10 RV Red RV-4 Murphy, Chris 173.00 199.09
376 Colorado 150 2009 7/23/09 RV Red RV-4 Murphy, Chris 172.90 198.97
279 Memphis 100 2008 10/19/08 RV Red RV-4 Murphy, Chris 172.78 198.83
487 Rocket 100 2009 11/22/09 RV Red RV-7A Reiley, Darrell 172.11 198.06
1098 Cleveland Texas Air Race 10/15/11 RV Red RV-8 Jones, Bryan 171.33 197.16
648 AirVenture Cup 2010 7/26/10 RV Red RV-3 Vasey, Bob 171.17 196.98
728 Grace Flight 2010 10/2/10 RV Red RV-7 Baker, Seth 171.00 196.77
845 Texoma 100, 2011 4/16/11 RV Red RV-4 Murphy, Chris 170.51 196.15
15 Taylor 100 2007 5/20/07 RV Red RV-4 Benton, Cam 170.43 196.13
703 Pagosa Springs 2010 9/26/10 RV Red RV-7 Baker, Seth 170.45 196.02
282 Memphis 100 2008 10/19/08 RV Red RV-4 Smith, Dwight 169.88 195.50
439 Pagosa Springs 100 2009 9/27/09 RV Red RV-4 Benton, Cam 169.78 195.25
16 Taylor 100 2007 5/20/07 RV Red RV-8 Jones, Bryan 169.45 195.00
760 Tennessee Valley Air Race 2010 10/30/10 RV Red RV-4 Archord, Jim 169.17 194.72
597 Sulphur Springs 130 7/18/10 RV Red RV-4 Benton, Cam 168.84 194.30
545 West Texas 100 6/6/10 RV Red RV-4 Murphy, Chris 167.83 193.14
923 Big Muddy, Carbondale, IL 6/4/11 RV Red RV-6 Weisgerber, David 167.82 193.12
704 Pagosa Springs 2010 9/26/10 RV Red RV-4 Faubion, Robert 167.80 192.97
546 West Texas 100 6/6/10 RV Red RV-4 Faubion, Robert 167.44 192.69
1511 Thunderbird Air Race, 2012 10/13/12 RV Red RV-6A Ahrens, David 167.42 192.66
1323 BSAR II, Three Forks, MT 7/7/12 RV Red RV-4 Keeler, Art 167.27 192.49
82 West Texas 100, 2007 10/7/07 RV Red RV-4 Benton, Cam 166.40 191.50
323 West Texas 100 2009 4/12/09 RV Red RV-4 Benton, Cam 166.29 191.36
239 AirCap 200 8/24/08 RV Red RV-6 Smith, Jim 166.21 191.27
504 Taylor 150 4/11/10 RV Red RV-7A Reiley, Darrell 165.94 190.96
184 Colorado 150, 2008 6/29/08 RV Red RV-4 Murphy, Chris 165.65 190.62
1100 Cleveland Texas Air Race 10/15/11 RV Red RV-6 Behrends, Steve 164.72 189.55
1128 Tennessee Valley Air Race IV 10/29/11 RV Red RV-4 Murphy, Chris 163.35 187.98
847 Texoma 100, 2011 4/16/11 RV Red RV-6 Smith, Jim 163.38 187.94
21 Taylor 100 2007 5/20/07 RV Red RV-3 Hackett, Willy 162.96 187.53
166 Denton 100 2008 6/15/08 RV Red RV-4 Bruggers, Ken 162.71 187.24
470 TVA II 2009 10/18/09 RV Red RV-6A Phillips, Mark 162.66 187.19
505 Taylor 150 4/11/10 RV Red RV-4 Faubion, Robert 162.24 186.71
144 Texoma 100, 2008 4/20/08 RV Red RV-6A Heathco, Charlie 161.75 186.17
549 West Texas 100 6/6/10 RV Red RV-7 Baker, Seth 161.58 185.94
668 Great Canadian Air Rally 2010 8/22/10 RV Red RV-9A Wilkinson, Greg 160.53 184.73
1544 Ozark Grove AR, Grove, OK 11/3/12 RV Red RV-6A Heathco, Charlie 160.07 184.21
1084 Northwoods 100 10/8/11 RV Red RV-9 Phillips, Tony 159.97 184.09
1105 Cleveland Texas Air Race 10/15/11 RV Red RV-6 Bivens, Darrell 159.35 183.38
106 Memphis 100, 2007 10/28/07 RV Red RV-4 Smith, Dwight 158.39 182.28
671 Great Canadian Air Rally 2010 8/22/10 RV Red RV-9A Murray, Charlie 158.29 182.15
1012 AirVenture Cup (TH) 2011 7/25/11 RV Red RV-4 Crawford, Tony 155.55 179.00
414 AirVenture Cup 2009 7/27/09 RV Red RV-3 Vasey, Bob 155.54 178.99
572 Top of the Chesapeake 7/11/10 RV Red RV-4 Winkelman, Steve 155.39 178.83
882 Lone Star Air Rally 5/14/11 RV Red RV-6A Bivens, Darrell 154.86 178.21
1221 Hill Country 150, 2012 4/21/12 RV Red RV-9A Johnson, Steve 154.33 177.60
1405 Pappy Boyington Memorial Cup 8/18/12 RV Red RV-6 Inkster, Ralph 153.42 176.56
564 Great NW Air Race 6/13/10 RV Red RV-6A Hungelmann, Bill 152.37 175.35
883 Lone Star Air Rally 5/14/11 RV Red RV-6A McGinnis, Patrick 144.92 166.77
418 AirVenture Cup 2009 7/27/09 RV Red RV-6 Campbell Steve & John Popel 138.33 159.19

Bob Axsom
 
Last edited:
BobTurner said:
Just to repeat others, there is something wrong with your TAS calculation. Your first post said 130 KTAS and a consistent 140 knots ground speed. No one is so lucky that they always have a 10 kt tailwind!
Click to expand...

What i was getting at was for these particular trips, the GS matched (the pitot wasn't clogged or frozen or anything like that)

Based on Bob Axsom's post, I need to talk to Chris Murphy
 
Last edited:
Sid Lambert said:
Ignore the EFIS. Fly the 3 or 4 heading test. Use the autopilot.
Click to expand...

Very interesting post to me since I just posted a question about something similar- I am purchasing a 180hp cs 6a and the skyview is giving me 161 ktas at 10,500 ft 2680 rpm 21" I wonder if the skyview numbers are inaccurate for various reasons as stated in other posts- so I asked my seller to go up and average gs four different directions. When he gets back to me ill post as well as get the other info for tas calculation- da oat etc.
 
You must log in or register to reply here.