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Seriously, I have a carb and not fuel injection. With the electronic ignition, P-mags in my case, I can run LoP. Down low I can't do it at WOT but at that altitude I could. When I did run it WOT, I couldn't get it to run smoothly. Bringing the throttle back a little bit smoothed it right out. I suspect that the reason was that having the butterfly valve partially closed caused the air to swirl just enough to improve the fuel distribution. On that flight, I was trying for max duration. So running at the lower fuel burn was a big help. Typically I would have to stop mid way to top off the tanks but because of the tailwinds and high TAS from being that high, I was able to land with a bunch of fuel left. (Shortly after I took that picture, I started downhill for home.) Here's a link to my write-up of that trip. |
Surprised that nobody has brought this up yet...
There are several aspects to short landings: steep descent, low speed, and deceleration. The bigger wing of the -9(A) gives you slow speed, the constant speed prop gives you drag (deceleration), on the approach, in the flare, and on rollout. On takeoff in my -9A, the % power indicator usually indicates in the high 70s. In other words, I'm taking off with maybe a tad less than 130 HP of the 160 HP that the engine is rated for. And the Sensenich prop has a 2600 RPM redline, so at cruise, I can't go full throttle, not to mention that in west Texas thermals, I'm always fussing with the throttle. In my book, constant speed prop is the way to go. I wish my -9A had one. Ed |
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This thread, combined with further research here, other sites, Van's, etc., brings me to this summary, as relates to the 3000nm AK trip. Assume two airplanes built per Van's recommendations, i.e., 160hp RV9 and 180hp RV7:
1) 100 mi range advantage 7. 2) 100 ft takeoff/landing distance advantage 9. 3) Cruise speed 10+ knots advantage 7. 4) 8 mph stall speed advantage 9. 5) The prices are almost identical, subject to prop choice. So the 9, with 20hp less, costs the same as the 7. What does the 9 give back in return for that 20ph? Because I'm a contrarian, I really want to prefer the 9 taildragger. But this morning's math is providing a hurdle. |
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low hours pilot
Question: At the altitudes he's going to want to fly over rough country given whatever the rocks reach up to and a likely preference for extra time should it get quiet in the cockpit, how happy is the 7 at 16500?
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Not Just Another 7 vs 9 Thread
[quote=StuBob;1235310]
So the 9, with 20hp less, costs the same as the 7. What does the 9 give back in return for that 20ph?[quote] The 9 gives back efficiency. Aircraft 7 9 Range 75% 775 710 Range 55% 950 860 Fuel cap USG 42 36 Miles/Gal 75% 18.5 19.7 Miles/Gal 55% 22.6 23.9 I found out long ago you can torture numbers to support one position or another. Try weighting your numbers to give more importance to the performance numbers you value most. Then pick the 9. |
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7 vs 9
Flown them both. Performance overall is pretty much the same when you average out minutes or dollars saved over several hundred hours. Acro of course means the 7. I prefer the way the 6 & 7 respond and handle when flying around for fun, but for long trips or occasional IFR the slightly less sensitive 9 handling is the ticket for me.
Don Broussard RV9 Rebuild in Progress 57 Pacer |
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That is just one reason. |
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When I was looking for a used kit, everything was on the table but I found a great deal on a -7A first. If I'd found a similar deal on a -9 first, I'd be flying it and be just as happy. I enjoy doing rolls and look forward to loops but that ability was not critical to my decision making. One advantage not mentioned about an A model is lower insurance cost. The tail-wheel folks (no offense intended) never seem to compare the number of ground loops with the number of nose gears that folded :D |
It?s a motivator to get me stay in the garage.
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Allan, what engine are you using to get that TAS?
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One of the strengths of the 9, IMHO, is the lower stall speed and all that implies. But you won?t find me ignoring the advice from Vans is it? A A pilot of an RV- 9A who is exceeding structural cruise speed, no matter how carefully and skillfully he flies, is not in control of the critical factors and is putting himself and his passengers at risk. Have a look at the advice on engine size before pushing the limits. If you are going into that territory you might be much safer in the 7 due to its extra strength. If you choose to fly close to VNE I hope your guardian angle or whoever looks after you is looking out for you. |
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Allan must have some tricks up his sleeve because my O-360 powered -9 tail dragger will hit the wall right at 200 MPH / 175 knots, which is just fine by me. His comments about flying high are right on the mark. Even at 17.5 the -9 is still flying nose down. Whereas the short wing RV's are flying nose up at those altitudes. |
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It?s not chance that link is only on the 9 page. The dangers are there for any aircraft but it?s a tighter corner for the 9. As for how Alan gets that extra 7mph. Well I?ve seen all sorts of things claimed on the internet, I certainly don?t believe it all. Let?s hope however it?s done that he has covered the dangers inherent in that speed in the 9. |
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performed many mods to add some extra strength in critical areas. We may offer some more of these mods on our website in the future. We see lots of interest in these, but are still in the testing stage at present. Thanks, Allan:D |
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[quote=tomww;1235892]The point is that those speeds are getting near the edge for the RV9. ... [/url]
Yep, they are close but not over. It is up to the pilot to manage the speed. Even an O-235 powered -9(A) can hit those numbers going downhill. |
AIRSPeed
Vno is indicated and Vne is true. Interesting huh?
Somewhere north of 8500ft, Indicated becomes secondary to True AIRSPeed. |
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Regarding smooth air......
The two worst turbulence events I have had in my flying career (both while flying RV's at high speed cruise and bad enough to cause major head impact on the canopy even with very tight belts) were surely encounters with wake turbulence, since the air had been glassy smooth for the previous 1/2 hr and it was for the half hour after the event.
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Hope the man who over stressed his 9 to 6G had it checked by a competent engineer. |
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...Yes! That would be me. Thanks, Allan..:rolleyes: |
The RV9 may not be the fastest model but I did outrun a M20C Mooney with 180 hp retractable gear and a cs prop with my fixed gear 150 hp and a fp prop, one person in each plane.
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Question for those that hit the canopy, do you have a 4 or 5 point harness, and how close were you to the canopy, almost 14 mod?
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