I wanna get high... No turbo though

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k9medic

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ATP-H, CMEL, CSEL, CFI/CFII Airplanes and Helicopters
I got to thinking about my "normal" flight profile in my Cherokee 6/260.

My trip is one non stop leg that is about 335nm. I normally cruise at 7000-9000' at full throttle and 2300 rpm on the prop. That gives me a fuel burn of just shy of 13 gallons per hour and I manage roughly 130kts TAS.

Looking through the horrible excuse for a manual, I am wondering if going up to 11K would be beneficial. The chart shows that I would theoretically be at 19.5 MP (which is still full throttle) and have to turn the prop up to 2400 rpm to get 65% power. I would think that my fuel burn would drop just a bit and I would pick up some TAS.

Not sure if the additional time to climb would negate the difference though.

Also not sure if I want to mess with O2 (I know it's not required but let's face it - it would make sense to use it for 2.5 hours at that altitude.)
 
I use O2 if I’m above 10k. Although technically my NA PA24 can get to FL210, above 13 or so, there are diminishing returns unless massive tailwinds are up there.
 
If you are still making 65% power, your fuel burn will be the same pretty much. You should gain a few knots TAS though.
 
I have always been able to make up any time lost in climb on the decent. I always just keep my power to roughly cruise rpm (fixed pitch prop) and just descend at a higher airspeed. Sure this won’t work for higher performance planes but has always worked in trainers for me. You can still make it a shallow decent too if you plan accordingly and start descending far enough away, you are just gonna be moving faster. Might neglect the fuel burn savings at alt but as far as speed goes it makes up for it.
 
You can always go to CO or WA
 
We all want to get high.
 
WannFly said:
You can always go to CO or WA
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Oregon too, er, wait, what are we talking about again?

I did actually take my plane to 17,500 after I bought it, just to see if I could and how it handled up there, did ok, as did I sucking on Oxygen.
 
Grum.Man said:
If you are still making 65% power, your fuel burn will be the same pretty much. You should gain a few knots TAS though.
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I agree with this. @k9medic , in my NA plane I find it doesn't make much sense to go above 10K unless you get a significant tailwind difference. Being an east of the Rockies guy, I don't like fooling with supplemental O2. I do plan on picking some up though because it is nice to have if getting up to 11-15K gets you above the tops sometimes.
 
Radar Contact said:
I agree with this. @k9medic , in my NA plane I find it doesn't make much sense to go above 10K unless you get a significant tailwind difference. Being an east of the Rockies guy, I don't like fooling with supplemental O2. I do plan on picking some up though because it is nice to have if getting up to 11-15K gets you above the tops sometimes.
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My experience as well.
With the modification that being a Rocky Mtn region pilot I carry O2 and will go well above 10k to clear the rocks when heading to the west.
 
NA Six 260? The power tables are fairly simple. You're not getting any TAS advantage at your peak 65% point, which would be full RPM circa 10K. That's fairly noisy to go just as slow as you would at 8K at a more pax friendly 2300 or 2400RPM. What cruising up there gets you is a smooth operation at 55% without the inefficiency of having the throttle plate part-closed. That thing climbs like a pig up there though, especially when loaded up with folks and their stuff. Hershey bar wing sucks at altitude, compared to the semi-tapered (*bigger wingspan, the airfoil is the same).

I've taken by NA Arrow II to 15K without too much fuss, but I'm running 6.5 gallons up there, going at Archer/Warrior speeds. It's rather pointless. You need a blower to make those altitudes worth your while with pax.
 
Is that ROP or LOP?

I think my RV10 is running the same engine (Lyc IO 540)? At 8 or 9K I’m < 11 GPH @ 22” and 2200RPM. That’s LOP.

In my case east of the Mississippi, only a stronger tailwind above 10 makes O2 worthwhile.




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I live in Colorado and there are times when I go to 15K to get over the "rocks" heading west or returning home. Forest fire smoke sometimes makes VFR difficult so to clear the "14-ers" I go as high as my non-turbo Arrow can go...which, in the summer, is about 16K. I use a PulseOximeter and my O2 bottle at those altitudes for sure!
 
Michael A said:
I always just keep my power to roughly cruise rpm (fixed pitch prop) and just descend at a higher airspeed.
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The biggest problem I have with highspeed descent is high rate of cylinder cooling and IAS going into yellow arc which is only allowed in smooth air .
 
Michael A said:
I have always been able to make up any time lost in climb on the decent.
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No doubt you get back some of the time lost on climb on the descent.

But not all, since drag increases geometrically at higher airspeeds.

Not saying it’s not rewarding to scream down in the descent at near cruise power. It’s what I do, just keeping an eye on staying out of the yellow arc.

As an aside, in my Cirrus I had a handful of flights at 17,500’. Calculating a 500 fpm descent had the plane in descent for over half an hour, and starting a long way out!
 
In the Venture I get 233 KTAS at 17k on 10-10.5 gph. At 8k I get around the same airspeed but on 13 gph. Granted I have to be going for max range to justify the climb but it gets there fairly quickly.
 
former Six owner here....and a 6/260 one at that. I never got any extra bang for the buck going higher. the plane lumbered along at anything higher than 8-9,000 feet. Just not enough power to go faster. The only reason for going high in your airplane is to get over weather or to catch an amazing tail wind. Both of those will take lots of time to get there....specially if you are heavy.

Your plane just isn't set up to go high....sorry. The highest I tried flying in my 6/260 six was 13,500 and it was slow at full power....and leaned for best power....probably burning somewhere around 11-12 gph. (don't recall) the last couple of thousand feet were at 200 fpm. and we were trying to get above the buildups on a summer afternoon along the east coast enroute from MD to Blacksburg VA.

My current plane has a turbo and climbs thru those altitude like no one's bidness....and holds the climb rate all the way up thru 20,000 feet. It burns the gas but also halls butt and trues out at 195Kts, There is no substitute for excess power....you quickly fall in love with it.
k9medic said:
I got to thinking about my "normal" flight profile in my Cherokee 6/260.

My trip is one non stop leg that is about 335nm. I normally cruise at 7000-9000' at full throttle and 2300 rpm on the prop. That gives me a fuel burn of just shy of 13 gallons per hour and I manage roughly 130kts TAS.

Looking through the horrible excuse for a manual, I am wondering if going up to 11K would be beneficial. The chart shows that I would theoretically be at 19.5 MP (which is still full throttle) and have to turn the prop up to 2400 rpm to get 65% power. I would think that my fuel burn would drop just a bit and I would pick up some TAS.

Not sure if the additional time to climb would negate the difference though.

Also not sure if I want to mess with O2 (I know it's not required but let's face it - it would make sense to use it for 2.5 hours at that altitude.)
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That’s kind of what I was figuring.

I lean using a egt and cht gauge keeping the temps below 1400 and 400 respectively along with a jpi fuel flow. That gets me around 12.5 gph in level flight.

I have only ever had to go over 9k once in this plane to get over some stuff. Miami center asked me if I would get up to 11k and I replied “eventually.”

Most of my flights are also within 150 lbs of max gross at take off so its a long slow climb.
 
When you’re leaning for best power and are above 8,000 feet you’re only making 65% or less power. So don’t worry about your temps. You can do no wrong. Plus EGTs are not an absolute temp but used for comparison. So go full throttle, butterfly open. Some say to pull it back a 1/4” in travel to allow the butterfly to cock some and create eddies or swirling for better fuel mixing/atomization. Then pull a little carb heat. Then lean and watch your airspeed max.at this point you will probably be at max EGT. But for that attitude and power setting it’s ok.
 
Checkout_my_Six said:
My current plane has a turbo and climbs thru those altitude like no one's bidness....and holds the climb rate all the way up thru 20,000 feet. It burns the gas but also halls butt and trues out at 195Kts, There is no substitute for excess power....you quickly fall in love with it.
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Yes, the turbo gives you lots of excess power as you get higher.

I’ve found my NA RV10 has plenty of excess power below 10k that makes a lot of SE US summer flying possible and pleasurable. Normal loading (2 people and 2.5 bags with full fuel = only 60gals) gives me good climb rates up to 9k to work my way around and over much of the weather. That 10.5 to 11.5 GPH at 155 to 163 knots is cost effective and comfortable for my typical 200 to 500NM trip.

I think I’d have to have a turbo to feel that good in the west but the combination I have has been keeping me happy for 8+ years now.

I thinking like the ‘10 compares well with the Six - faster but lacking a bit of load hauling. I tend to run out of cabin volume before gross weight, but no CG problems thankfully. Fixed gear is nice.


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The ten is faster... but the Six is hauling 1,550 lbs. the Ten does that? Bet not. And the cabin volume in the Six can not be beat by any single. It’s huge. That’s what folks love. And are willing to compromise speed and fuel burn for the space and baggage area.

Full disclosure... the turbo ain’t just for climbing mountains...it’s a wonderful east coast plane and does great for getting on top of the clag to navigate the buildups in the summer and get above the ice in the winter.
 
Michael A said:
I have always been able to make up any time lost in climb on the decent. I always just keep my power to roughly cruise rpm (fixed pitch prop) and just descend at a higher airspeed. Sure this won’t work for higher performance planes but has always worked in trainers for me. You can still make it a shallow decent too if you plan accordingly and start descending far enough away, you are just gonna be moving faster. Might neglect the fuel burn savings at alt but as far as speed goes it makes up for it.
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I read something long ago that the most efficient way is to never level off. Climb shallow with more forward speed until the halfway point then descend that way to destination. Obviously not practical in real life most of the time. But I wonder if it's true.
 
Grum.Man said:
In the Venture I get 233 KTAS at 17k on 10-10.5 gph. At 8k I get around the same airspeed but on 13 gph. Granted I have to be going for max range to justify the climb but it gets there fairly quickly.
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What’s your range on that thing?
 
k9medic said:
My trip is one non stop leg that is about 335nm. I normally cruise at 7000-9000' at full throttle and 2300 rpm on the prop. That gives me a fuel burn of just shy of 13 gallons per hour and I manage roughly 130kts TAS.

Looking through the horrible excuse for a manual, I am wondering if going up to 11K would be beneficial. The chart shows that I would theoretically be at 19.5 MP (which is still full throttle) and have to turn the prop up to 2400 rpm to get 65% power. I would think that my fuel burn would drop just a bit and I would pick up some TAS.

Not sure if the additional time to climb would negate the difference though.
Click to expand...

The best tool for this, IMO, is the Performance subscription to ForeFlight. That already has your flight manual performance charts baked into it, and it will be considering winds aloft as well, including during the climb and descent.

You can use your flight manual and figure this all out, but doing the winds aloft for climb and descent is really time-consuming, not to mention at least a little bit difficult... And you won't have ForeFlight's wind model, which is much more granular than you get from the official briefing sources. To me, it's still a fun exercise to do it, but I have a somewhat twisted definition of "fun". ;)

FWIW, like any normally aspirated airplane with a constant speed prop, my optimum speed altitude for 65% is also around 9,000. There, I'll true about 175 on 12 gph. But, I did have a leg where I needed to go to 13,000 at the beginning for terrain so I just threw the cannulas on and stayed there, and I trued 172 on 10.1 gph. If you have a decent tailwind, the speed difference is pretty negligible but it'll save you a fair amount of fuel.
 
Grum.Man said:
I play it pretty conservative and call it 900 miles. It will do 1000 if I really pull it back but the added time cost more than a fuel stop.
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That thing looks awesome. Any difficulty finding parts? I am hearing there are only 30 flying in the US...
 
Not yet. The guys that own the company now have a few spares still and a few complete kits. I’ve reverse engineered a few of the more complex cast parts and machines them from billet aluminum.
 
dans2992 said:
That thing looks awesome. Any difficulty finding parts? I am hearing there are only 30 flying in the US...
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Its EAB. hens teeth's not nearly a problem as the certified counterpart.
 
Checkout_my_Six said:
The ten is faster... but the Six is hauling 1,550 lbs. the Ten does that? Bet not. And the cabin volume in the Six can not be beat by any single. It’s huge. That’s what folks love. And are willing to compromise speed and fuel burn for the space and baggage area.
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Yep. With full fuel (6 hours worth) I can still pack 997 lbs of stuff in the plane. I can drop it back to 4 hours of fuel and take 1153 lbs if I want to.
 
I’m my NA bonanza, 8-9k on a XC is the sweet spot. We run LOP. Higher or lower only due to weather. I use FlyQ and let it do the heavy lifting for best alt for climb, winds, decent, etc. no extra subscription required.
 
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