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What about flying an RV slow?

claycookiemonster

Well Known Member
Chatting with a Kitfox builder today. Both of us are hoping to be finished and flying in the summer of '23. He said, "We should fly to Oshkosh together to celebrate!" It sounded fun, but then I began to wonder about flying along with a 100kt airplane from Utah to OSH.

How are RV's at slow and leisurely cross country flying to pair up with a Kitfox or Cub?
 
Doable, but methinks you will get pretty bored.

However, it will be great practice for flying the conga line at OSH arrival.
 
Just give him a head start for each leg and then have the coffee ready for when he lands, he might appreciate that.
 
I lead a flight of four Stearmans at 80 KIAS. Flying halfway across the country at 100 knots sounds painful and expensive.
 
How are RV's at slow and leisurely cross country flying to pair up with a Kitfox or Cub?

The wonderful thing about an RV is that flies very nicely at any speed (within its limits). I fly my RV-4 with a few slower aircraft (i.e. Carbon Cub, Murphy Rebel) and it is fine for a short while. With the rpm under 2000, I quickly start looking for more temperature and end up flying a lot of circles around them - probably end up flying twice as far as they do. Also fly with some faster but still slow-ish aircraft (i.e. RV-12, Bearhawk, C-195) and at least that feels like moving forward. I once escorted a C-182 from New Mexico to Idaho and I thought that trip was never going to end. On a positive note, I was not 'overworking' the engine! ;-)

The issue, IMO, is engine temps. Per Mike Busch's article on recommended temperatures and sticking valves (https://www.youtube.com/watch?v=7ohsVvYbAaQ), I don't like running super slow for long periods due to the very low CHT's. During the cooler months, my CHT's can drop to 250 degrees when flying with slow aircraft.
 
Watch the temps

I found that when flying too slow I have to keep an eye on the oil temps. When I have the plane rocked back it just feels weird and if the OAT is up there, the oil temps get too high. I had to follow a Stearman in an extended pattern one day and I didn't like it at all. There is no way I'd fly that far at 80 knots.

Tell your friend you'll save him a spot and fly at "normal" speed.

-Marc
 
Just give him a head start for each leg and then have the coffee ready for when he lands, he might appreciate that.

Agree that is the way to go. He can give you pilot reports for first half of each leg and you provide them for the second half. Pick an air to air frequency to talk over and it will feel like you are flying a very loose formation.
Best part for you will be half way through each leg when you pass him like he is standing still.
 
Unless Your Goal is Just to “Get There”

If you really love to fly…The slower you fly, the more time you get to fly (is that physics??). Get to see more as well.
Not so long ago, a group of pro jet jockeys out of PTK flew their cubs, luscombes, and citabrias from the headwaters of the Mississippi all the way down to the gulf. Took a few weeks. If something like that doesn’t make you envious, you need to turn in your certificate.
Terry CFI
RV9A N323TP
 
I found that when flying too slow I have to keep an eye on the oil temps. When I have the plane rocked back it just feels weird and if the OAT is up there, the oil temps get too high. I had to follow a Stearman in an extended pattern one day and I didn't like it at all. There is no way I'd fly that far at 80 knots.

Tell your friend you'll save him a spot and fly at "normal" speed.

-Marc

Have flown my RV-6 with a Kitfox a number of years ago for almost an hour. Marc hit the main problem my airplane had doing this. At the lower speed on the back side of the power curve, there is not enough cooling air to keep things where I want them.

I frequently fly by myself at 2,100 RPM and 22 inches. That give me right at 122 KIAS and 6 GPH or less fuel burn. In my airplane, that is a very comfortable power setting.
 
Enjoy it!

Why not? I fly navigation rallies with my Mooney at 90 knots. It’s fun, and the slower you fly the more time you have to find the targets on the ground, or in your case to enjoy the landscape.
 
You RV can fly slow no problem, but your Lycoming is another issue. Assuming you will be burining 100LL, flying that slow for extended periods you will be accumulating lead build-up in the engine. You will also find that you get horrable fuel efficency.
When I fly long distances with my kids (flying a Tomahawk) I let them leave before me, and plan on passing them at the 1/2 way point. This way we are able to stay in almost constant raido contact.
 
great post. I suggest you give it a try and report back with your experience. definitely doable. ;)
 
Awesome insights, all. Sleeping late and leaving behind him, and then waiting for him on the ramp with coffee at the end sounds perfect.
 
Find what your best MPG speed/power setting is, and fly that. You'll still be faster than him at that power setting, but if you let him depart first and land last, you will have a little time to help with logistics on both ends as a favor.

Really, doing that along with finding each other/joining up for a bit in the middle of each leg just for fun - I bet you won't find yourself waiting for him all that long at each stop. You'll stay entertained and fly efficiently. Plus the trip will be a great example of enjoying the getting there over just getting there.
 
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I frequently fly by myself at 2,100 RPM and 22 inches. That give me right at 122 KIAS and 6 GPH or less fuel burn. In my airplane, that is a very comfortable power setting.

Hopefully you're not flying in a prop 'restricted' range, most Lyc publications list 2350 as the lower limit on RPM for cruise with a 360 for what it's worth.
Most of the Hartzell prop restrictions are for 2100-2350, likely because there are more harmonics down that low.
 
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Hopefully you're not flying in a prop 'restricted' range, most Lyc publications list 2350 as the lower limit on RPM for cruise with a 360 for what it's worth.
Most of the Hartzell prop restrictions are for 2100-2350, likely because there are more harmonics down that low.

Hi Walt, I've got the io-360 from Mattituck, pmags, FM-200, and the Hartzell 2-blade C2YR-1BFP/F74972 metal prop. I can't find any RPM restrictions, but it does feel like there are some vibrations when I go below about 2200. I thought it might just be prop balancing, which I plan to do soon. Mine feels smooth above 2200, and when I'm in "slow cruise" I'm usually at 2250. While I can't seem to find a specific RPM restriction, I am curious if there are some recommendations to avoid particular RPMs due to harmonics. It seems that this combination must be pretty-well researched, so I doubt I'm breaking much new ground with this question. Thanks for any insights.
 
Hi Walt, I've got the io-360 from Mattituck, pmags, FM-200, and the Hartzell 2-blade C2YR-1BFP/F74972 metal prop. I can't find any RPM restrictions, but it does feel like there are some vibrations when I go below about 2200. I thought it might just be prop balancing, which I plan to do soon. Mine feels smooth above 2200, and when I'm in "slow cruise" I'm usually at 2250. While I can't seem to find a specific RPM restriction, I am curious if there are some recommendations to avoid particular RPMs due to harmonics. It seems that this combination must be pretty-well researched, so I doubt I'm breaking much new ground with this question. Thanks for any insights.

No limitations on that prop with standard mags and compression (assuming 180hp 360), not aware if Hartzell has done any testing with dual Pmags though.
 
At 45% power with 2000 RPM I burn 6 GPH and indicate like 123 kts with reduced noise levels. At this lower RPM the oil temperature is actually lower despite the lower speed. My engine(s) don´t like power settings below 40%.
 
Low temps

Very gratifying to hear someone who understands how damaging low temperatures can be, CHT and Oil.
 
Hi Walt, I've got the io-360 from Mattituck, pmags, FM-200, and the Hartzell 2-blade C2YR-1BFP/F74972 metal prop. I can't find any RPM restrictions, but it does feel like there are some vibrations when I go below about 2200. I thought it might just be prop balancing, which I plan to do soon. Mine feels smooth above 2200, and when I'm in "slow cruise" I'm usually at 2250. While I can't seem to find a specific RPM restriction, I am curious if there are some recommendations to avoid particular RPMs due to harmonics. It seems that this combination must be pretty-well researched, so I doubt I'm breaking much new ground with this question. Thanks for any insights.

For my prop, the minimum speed limitation is 2350 rpm for MP > 22”. I run it slower than this during cruise but only when MP < 22”.
 
Clay,
Went out for a post maintenance test flight today and decided to test oil temp vs low airspeed while I was at it.
RV-6A with O-360
Oil temp started at 178F after departure and exiting under Class B airspace at 120 KIAS or so.
95 KIAS - 5300' MSL - 2300 RPM
Oil temp peaked at 201F after 20 minutes at the above parameters.
CHT's were around 350F.
You'll just have to see how your airplane behaves.
 
I flew from Atlanta to SunNFun last year with a Sling at about 135 mph in formation. I let him lead and adjusted to his speed. After getting adjusted to the right settings, I appreciated the smoothness and relative quiet of going that slow. He was all out max burning 10 gph with his Rotax while I was burning 4.8 gph matching this speed. I can’t say it was the most exciting leg of the trip but all worked out well.
 
I flew from Atlanta to SunNFun last year with a Sling at about 135 mph in formation. I let him lead and adjusted to his speed. After getting adjusted to the right settings, I appreciated the smoothness and relative quiet of going that slow. He was all out max burning 10 gph with his Rotax while I was burning 4.8 gph matching this speed. I can’t say it was the most exciting leg of the trip but all worked out well.

Rotax 912 fuel consumption at cruise settings should normally be 18-20 litres per hour, i.e 4.5-5 gph.
 
Hopefully you're not flying in a prop 'restricted' range, most Lyc publications list 2350 as the lower limit on RPM for cruise with a 360 for what it's worth.
Most of the Hartzell prop restrictions are for 2100-2350, likely because there are more harmonics down that low.

There are no restriction on the 7663 blade and Hartzell hub on the 320 / 160 HP Lycoming engines. TCDS P-920

I am using an old LASAR ignition system that is frequently placed in MAG ignition mode (LASAR turned off) so as to avoid overheating issues.
 
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Rotax 912 fuel consumption at cruise settings should normally be 18-20 litres per hour, i.e 4.5-5 gph.

Yeah but he’s talking about the Rotax running all out.. I’ve seen 7.4 or so full out on a 100hp rotax.. if he was seeing 10 GPH, I wonder if it was turbo?
 
Flying slow

I once ferried a Rans S7 from Detroit to upstate NY.Accompanying me was an RV6 who entertained himself by flying big circles around my slow Rans and doing other aerobatic maneuvers.Was entertaining to watch,but was a painfully slow ride otherwise.
 
Yeah but he’s talking about the Rotax running all out.. I’ve seen 7.4 or so full out on a 100hp rotax.. if he was seeing 10 GPH, I wonder if it was turbo?

If it was a turbo Rotax 914 all out in a Tsi then it would be going much faster than 135 mph.
The Rotax 912 has a limit of 5 minutes at max power and even then it would be below 30 lph.
There must be a typo in the post, 10 gph does not sound right. Sling 2 seater performance is similar to RV-12 cruising at 120 knots should be around 5 gph +/-.
 
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