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  #1  
Old 12-12-2017, 08:45 PM
iaw4 iaw4 is offline
 
Join Date: Sep 2015
Location: Los Angeles, ca
Posts: 11
Default 130 IAS at 5000' and 8gph fuel flow

I am thinking of buying someone's RV-9A. I am concerned that there seem to be wide variations in performance. ideally, the builder would quote me performance numbers at 8,000'--for comparison to the Vans demonstrator and other postings--but he does not have them and I think he has stopped flying, so he cannot easily get them.

he does say that he used to cruise at 130 IAS at 5000-6000' with 8gph fuel flow. for those of you who are flying one and know performance both at 5000' and at 8000', is this great, good, average, bad, or terrible? (ideally, can you please post some IAS's at 5000' and 8000', with rpm setting and fuel flow, so that I know how to scale the numbers?)

help appreciated.

regards,

/iaw
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  #2  
Old 12-12-2017, 09:03 PM
YellowJacket RV9 YellowJacket RV9 is online now
 
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There really isn't enough data here to properly assess it. First off, are we talking MPH or knots? IAS doesn't mean much and can vary depending on installation. A quick estimate at 5000' standard pressure and 68* OAT converts 130 knots indicated to 144 true, but again, that doesn't account for installation differences. 8GPH would be a pretty high cruise power fuel flow for me.

Again, it may be easier for you to specify the engine and prop on the airplane, and people with similar combos can give you a good idea of expected performance. Searching for 9A performance will also bring up a bunch of threads with that info. I have an O-320 150HP and sensenich fixed pitch metal prop. I flight plan at 140 knots and 7GPH. I am usually a bit faster than that, and usually fly above 8-10k', where the plane is most efficient. 14,500', wide open throttle, I am around 142 knots true at 6-6.5GPH. That's rich of peak - I am still playing with getting it to run well LOP.

Chris
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Last edited by YellowJacket RV9 : 12-12-2017 at 09:06 PM.
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  #3  
Old 12-12-2017, 09:08 PM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
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In addition to what Chris said, the builder's performance measurements may be accurate, or they may not be.

Is his fuel flow calibrated? How about his tachometer and ASI? I'd say the performance figures the builder quoted are slightly below normal for an RV-9 <assuming the builder was using Knots as a reference), but who knows what prop the airplane has, what engine (a low compression engine will burn more fuel for the same power), etc.

There are lots of builders and pilots out there who don't have good data on their aircraft's performance.

By the way, here's a TAS calculator if you'd like to calculate the impact pressure and temperature have on TAS:

https://www.dauntless-soft.com/produ...eedCalculator/
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  #4  
Old 12-12-2017, 09:08 PM
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Dbro172 Dbro172 is offline
 
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Location: West Fargo, ND
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I rarely see IAS in knots above the 130ís in cruise. Typical KTAS in cruise at 8 gph is around 150 +/-. In the cold air now I can easily get in the yellow arc at low altitudes. Top end is 160 KTAS plus, but nobody really flies around at low altitudes, fire walled and/or max rpm do they? Would be helpful to know what engine / prop combination it is and from that we can tell you what to expect performance wise.
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  #5  
Old 12-13-2017, 07:01 AM
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petehowell petehowell is offline
 
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Location: MN
Posts: 2,144
Default Performance History

Here is the thread where I document my numbers on a sorta yearly basis - not the altitudes you wanted, but might be of some help.
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  #6  
Old 12-13-2017, 12:58 PM
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PerfTech PerfTech is offline
 
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Default My Typical Numbers!

... Here is a shot of the numbers that I typically see in economy cruise.
This fight was at 8500ft. but can still provide you with a lot of information.
The typical fuel burn is 6.8 GPH at this altitude and speed. If I climb to
say 1,4000K I can go about 8 KTS faster (all speeds are in KTS) with no
fuel penalty, or, push in a little more power to increase the speed with
about a 7.8 GPH fuel burn. I really love my RV-9A, and I feel this is the
best model for my purposes. Thanks, Allan..

Add on info; My RV-9A has a 0-320, stock 8.5 to 1 CR, Carbureted, one
mag & one Light speed ign,160 HP, Whirlwind C/S 986LB.

https://photos.google.com/photo/AF1Q...MJLd7QuT_EjoQ_
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Last edited by PerfTech : 12-13-2017 at 03:36 PM. Reason: left off some info.
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  #7  
Old 12-13-2017, 02:40 PM
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RVbySDI RVbySDI is offline
 
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Ok, I am not sure I can give an educated opinion on the plane you are looking into buying. However, I can give you some info concerning what I see with my 9A. Here are a couple of pics of past flights. Both flights are running LOP so, as a side note to anyone wondering about what these engines are like running LOP, well, you might want to look at the CHT temps on both flights. Just sayin'!



To familiarize you with the readout: True airspeed (TAS) - top left corner (171 mph); Indicated airspeed (IAS)- left tape (152 mph); Altitude - right tape (8500 ft); Density altitude - bottom left with label D Alt (7916 ft); fuel flow - just above the MAP dial bottom right (7.4 gph). One item of interest to note. Notice the GPS ground speed? Yep, 100 mph. Had a heck of a headwind that day! Yikes!!

Now that you are familiar with where to see the data on my displays, here is another flight.


A couple of differences to note on this flight. Notice this one I am cruising 2K higher, but look at the D Alt. The speed is showing IAS as 6 mph SLOWER than the above flight but notice my TAS. It is actually 6 mph FASTER than the above flight. Pretty interesting! But not as interesting as the fuel flow. Notice that difference? I consider anything 10,500 or higher to be settling into the wheelhouse for the 9(A). Because of that, I would say that the plane you are looking at may not be performing its best at 5,000 ft. However, as others have said, we need more data to really say much about it.

As for what is in my 9A: ECI IO-340 9.1:1 pistons (180 hp), forward facing cold air induction, Plasma II Lightspeed Electronic Ignition + Slick Mag, 4-straight pipe, Catto 72 X 74 3-blade prop.

Oh, and lastly, what it says on the link in my signature below.
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  #8  
Old 12-13-2017, 02:49 PM
YellowJacket RV9 YellowJacket RV9 is online now
 
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Quote:
Originally Posted by RVbySDI View Post
I consider anything 10,500 or higher to be settling into the wheelhouse for the 9(A).
Agreed. Van's plans for the 9's ought to include built-in O2, as up high is really where it is meant to be. I try to get over 10k for all but the shortest trips.

Chris
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  #9  
Old 12-13-2017, 03:12 PM
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Dugaru Dugaru is offline
 
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I'm starting to explore higher altitudes in my (relatively) new (to me) RV-9A. I've got O2. Over what distances do you think it makes sense to climb to 10K or more?

Quote:
Originally Posted by YellowJacket RV9 View Post
Agreed. Van's plans for the 9's ought to include built-in O2, as up high is really where it is meant to be. I try to get over 10k for all but the shortest trips.

Chris
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  #10  
Old 12-13-2017, 03:21 PM
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airguy airguy is offline
 
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Quote:
Originally Posted by Dugaru View Post
I'm starting to explore higher altitudes in my (relatively) new (to me) RV-9A. I've got O2. Over what distances do you think it makes sense to climb to 10K or more?
I do it on just about anything over about 75 miles, just because it's so easy to do. For 150 miles or better I just stick it up there to 16,500 or 17,500 and turn on the oxygen. There's virtually no traffic up there, it's cool and smooth, the radio reaches out to forever, visibility is great, and you can glide for a long time on an engine-out scenario which enhances safety.

I don't try to rationalize climbing up there by virtue of fuel economy or time spent in the air or anything like that. I rationalize it exactly the same way I rationalize ownership of an airplane - I do it because I can.
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Built an off-plan 9A with too much fuel and too much HP. Should drop dead any minute now.
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