apkp777

apkp777

Well Known Member
Had someone ask me today "how high can you fly?". I told him, I have no idea. Van's lists the ceiling for an RV9 with 160 HP at 24.5k. I wonder? Some of the MEA's in the Rockies are above 14k. I know that I should have no problem with that, but it begs the question - How high have you flown in your RV?
 
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apkp777 said:
...How how have you flown in your RV?
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Terry Jantzi has been to about 26,000. http://fly.hiwaay.net/~sbuc/journal/high.html

Personally, I have never been into the flight levels.

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206 knots groundspeed at 17,500 in the middle of summer.
 
17.5 is pretty good. Very interesting article Terry wrote about getting to 26k. For non-turbo that's pretty good I'd say.
 
No contest, if you include "modified" RV's....Bruce Bohanon, RV-4/8, "Flying Tiger"....49,000 and change!
 
I flew my RV-4 w/160 CS at 17 and 18K all the time.... 5gph 155KTAS. over 30 nm/gallon!!!! it was still climbing in the 500 fpm range solo...

The Rocket is still in the 7-800 fpm range at 120 KIAS between 17 and 18K... It will do 200 KTAS on 10 GPH, 20 nm/gallon, still not bad for 230 mph!!!! Put a 40 kt tailwind behind you, and fly for 4 hours and you are along ways from home!!!! I do have to watch the CHTs in the climb however, they will get over 400 very easily if you get slow or get stingy with the gas.....

The EVO would make FL 300 with no trouble I am certain... But I don't have an A-12 regulator to get there....

Tailwinds,
Doug Rozendaal
 
did some testing..........

i did an altitude test years ago when i got a o2 bottle. 1,000fpm to 12,000' then 500 fpm to 17,999'. 180 hp 6a cs. awesome view from there. should of shut down and glided back. love them RV's. turbo
 
Something about flying that high just makes me quiver. Thoughts of Mike Adams in the x-15 sub orbiter spinning at 230,000 while descending goes through my mind. Yeah, I am a wuss! But you can be sure, I am going to file an IFR flight plan for FL18 or FL19 in my -9. Something about reading back my clearance "climb 3000, then expect FL 18 one zero minutes after departure" that is freaking awesome. Especially when at FL 18 you tell the controller, "hey, I getting a bit of chop, would like to request higher!"
 
MCB - Shows how often I have flown the flight levels, uh once!

Yes FL 180 or FL 190 here we come!
 
SkywayCaptain said:
Here is a report of what happened to a local pilot who liked to fly in the flight levels in unpressurized aircraft.

http://ntsb.gov/ntsb/brief.asp?ev_id=20090731X10108&key=1

Make sure your oxygen system is up to the task.
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What a sad read that was. Jeez!! I would think O2 gauge/level check would be in the preflight checklist. I wouldn't know as I never needed o2 in my training :) . High altitude flight will be part of my routine flying once my -10 is done.
 
SkywayCaptain said:
Here is a report of what happened to a local pilot who liked to fly in the flight levels in unpressurized aircraft.

http://ntsb.gov/ntsb/brief.asp?ev_id=20090731X10108&key=1

Make sure your oxygen system is up to the task.
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It doesn't appear that a probable cause has actually been determined yet. Although the O2 system is an obvious suspect sounds like a medical problem also might be possible?

I'm curious what percentage of RV pilots use a pulse oximeter when flying in the teens?
 
I have had my RV-7 fixed pitch sensenich and dual light speed ignition and carburated engine to 25,500 in July. It didn't want to climb any higher.
 
It is hard to say what happened to the Cirrus pilot, but it sounds like hypoxia due to whatever reason to me. I would not want to fly an unpressurized aircraft above FL180 without a demand type mask. My RV has oxygen with cannulas and a pulse oximeter. I don't fly the RV above 12,500ft unless I have a REALLY good reason, like mountains and then for minimum durations. I do most of my flying for work, pressurized, above FL400.
 
Sounds like Norman - Has the top spot for N.A. FP at 25.5K.

I like to hear all the details of that flight, how long did it take, what were the controls like. Etc?
 
Makes me think more of how nice it would be to have a "dead man's failsafe" on an auto-pilot, to auto-descend to a preset altitude if it wasn't reset every XX minutes. Of course...adding that and the auto-throttles would add a whole new layer of complexity probably more likely to cause issues than the problem it would address...but interesting to think about.
 
apkp777 said:
Sounds like Norman - Has the top spot for N.A. FP at 25.5K.

I like to hear all the details of that flight, how long did it take, what were the controls like. Etc?
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It was several summers ago that I made this flight. I don't recall how long it took to get up there but I was still climbing at 500ft/min at 20,000. I had full tanks on take off and about 30 pounds of baggage and I was by myself at 160 pounds. The aircraft empty weight was 1085 pounds. The guys in the CYVR ATC had a bet on how high I could get. They asked my what my climb rate at 20k was and I told them and they said that what there read out was telling them. The operator was crying the blues because he said his C172 had a hard time doing that on a hot summer day at sea-level. I can't remember what the IAS was, pretty low. At 25,500 the controls were very sensitive and the plane felt like it was resting on a knife edge in all three axis. I couldn't coach any more out of it. The last 500 ft was pretty slow. I have an section of airspace that I can activate for making such tests here without having to file IFR.
 
Norman CYYJ said:
At 25,500 the controls were very sensitive and the plane felt like it was resting on a knife edge in all three axis.
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Hi Norman, I'm curious about this...I would have anticipated the thinner air causing the controls to be sluggish. What makes it this sensitive?
 
lostpilot28 said:
Hi Norman, I'm curious about this...I would have anticipated the thinner air causing the controls to be sluggish. What makes it this sensitive?
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Not Norman, but I've flown RV's pretty high....the problem is that you are right on the edge of a stall at the fastest speed you can maintain. Think about the fact that with constant IAS, the TAS goes down with altitude. Sooner or later, the highest IAS you can get is stall speed. It's like balancing on top of a ball - easy to fall off!
 
Wrong choice of words about being sensitive. Sensitive to keep the plane straight and level without it stalling. Maybe with a constant speed prop I could have got a bit higher but there was a definite lack of rpm and power.
 
Ironflight said:
Not Norman, but I've flown RV's pretty high....the problem is that you are right on the edge of a stall at the fastest speed you can maintain. Think about the fact that with constant IAS, the TAS goes down with altitude. Sooner or later, the highest IAS you can get is stall speed. It's like balancing on top of a ball - easy to fall off!
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Coffin Corner in an RV? Huh, who'd a thunk it.

I've only had mine up to 14.5K on a reaaally bumpy day... it didn't like it much and I had to drop back down to 12.5 to stay happy and I haven't been back up high yet to try it again.
 
Ironflight said:
Not Norman, but I've flown RV's pretty high....the problem is that you are right on the edge of a stall at the fastest speed you can maintain. Think about the fact that with constant IAS, the TAS goes down with altitude. Sooner or later, the highest IAS you can get is stall speed. It's like balancing on top of a ball - easy to fall off!
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Hi Paul, I think thats the other way around...but this still leaves a bit of a question because even at 25,000 feet, if you're TAS is 120 mph, you should be indicating 80 mph. Is this an instance of a high AOA to maintain your altitude (with a very slow airspeed)?
 
I'm afraid I will have to disagree with Paul on this one. At the absolute ceiling of a normally asperated piston engined airplane, the speed for Vy and the speed for Vx will both be the same, and will be the only speed for which the airplane can maintain that altitude. In an airplane like an RV, it is well above stall speed.

I tested my RV-8 to its absolute ceiling of 24,300 ft. At the weight and CG used, the only speed which would hold altitude was 87 kts. At 88 kts, the airplane would decend, and at 86 kts the airplane would decend. Stall speed at the same loading is about 53 kts.

All above speeds are of course indicated, and I am sure Paul meant TAS would be higher than IAS.

Pat
 
Yup, I wrote it backwards, but the concept of the "coffin corner" is still sorta what I was trying to get across - the airplane just gets very touchy at that point - like flying slow flight.
 
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Ironflight said:
Yup, I wrote it backwards, but the concept of the "coffin corner" is still sorta what I was trying to get across - the airplane just gets very touchy at that point - like flying slow flight.
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Your description of feeling like you are balancing on a ball describes it quite well. I have never had the same feeling in a plane down low in slow flight or flying just a hair above the stall, its not quite the same experience.
 
Flying a little higher than before...

I've never been above 11,050 feet. That's the highest I could get my Continental C-85 powered Dakota Hawk to fly. At that altitude, the controls felt mushy, and I wasn't comfortable being there. In fact, there was very little reason to be there since it took so long to get to that altitude that I almost immediately had to descend to get more gas!

Now, with a little more speed and power in my RV-7, I'm thinking that there may be advantages to flying in the 10 - 15,000 ft range. I've been looking at O2 systems, and I know all of the LEGAL sides about O2, as well as the AGE and HEALTH RELATED MEDICAL sides that recommend O2 at even lower altitudes if necessary. So let's just leave O2 completely out of this question!

So...

What is the greatest benefit to flying higher? Is it improved economy, less traffic, better ground speed?

What is the trade-off? Is it less control feel, length of each leg, or something else?

What is the break even point for, say, a climb to 10k? Would you climb to 10k for a one-hour cross country? A two-hour cross country? Three?
 
The Wife & I frequently fly from the Seattle area to Eastern Washington. 10,000 ft is normal. Fisrt we climb to clear the Cascade mountains, then Mt Stewart, after that it's for the usual tail wind and a smoother flight. The Cessna 172 stuggled the last few thousand feet.
Then we got a Cessna 182, what a welcome improvement all the way around.
Don't let anyone try to tell you a big engine 172 or 175 'is the same as'.
I'm so looking forward to finishing the RV-8. :D
 
Sparky Imeson recommends, in his Mountain Flying Handbook, not to climb more than 10 minutes for each hour of en-route flight time.
He also suggests that the most efficient and economical altitude would relate to the full throttle position for the power setting you desire on the flight. e.g. You choose to fly at 75% power, fly at the altitude where full throttle travel would produce 75% power. Any higher wastes time/fuel in getting there and any lower sacrifices performance.
 
AndyGilbert said:
Sparky Imeson recommends, in his Mountain Flying Handbook, not to climb more than 10 minutes for each hour of en-route flight time.
He also suggests that the most efficient and economical altitude would relate to the full throttle position for the power setting you desire on the flight. e.g. You choose to fly at 75% power, fly at the altitude where full throttle travel would produce 75% power. Any higher wastes time/fuel in getting there and any lower sacrifices performance.
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Interesting...I'm gonna grab a copy of the ref and give 'er a read (not a bad idea since I live in the mountains! ;)) Honestly not trying to beat up your first post (welcome, by the way!)...just musing on this a bit, as I always want to learn (and you're a career CFI!), and economical cruise is near and dear to the hearts of many here! It is to mine, as 38 gallons and a big motor make fuel planning a big item for me.

My first thought was that the two rules of thumb you mention are pretty general, especially for a mountain flying manual. No matter how far I was flying, or how long the climb takes, or what the WOT power setting was at the cruise altitude, I'd want to climb to where the rocks were no longer a factor, the ride was good and the tailwind (if applicable) was optimum (all things Scott mentioned above).

However, in thinking about it, the first "rule" may not be much of a restriction in an RV...should be able to climb quite high in "10 minutes per hour of cruise"...unless you're really heavy, or on the lee side of the rocks and fighting your way uphill. Might be a stretch for an aircraft with lesser performance though.

Wondering if the second rule applies more to FP props, since you can get a large variance of %HP (at a given altitude) at WOT by changing RPM with a CS prop.

There probably is an optimum climb/cruise/descent profile for a given stage length, and it probably changes with a headwind or tailwind. I'm actually looking for a speed and range/endurance maximizing profile for Airventure Cup this year. Max Speed/Range, or Max Speed/Endurance is an unusual combo (often mutually exclusive), but 376NM at WOT and max RPM is going to stretch me hard, so I need to find out how much tailwind I need, what altitude I need to climb to (and how I need to climb to it), to be able to leave the hammer down and the "balls to the wall", and under what wind/altitude conditions I need to sacrifice speed for landing with legal reserves. Any thoughts from the braintrust? Bob Ax, any secrets?

And to go back OT, Scott, the first time you do that trip in your 8, you'll probably pinch yourself and say, Yeah Baby!! :) I just came back from Central Cal to Reno, and was getting bopped at 10.5, so I popped up to 12.5 and the RV didn't even breath hard at either altitude...I think it looked at me and said, "Is that all you need? C'mon, work me a bit!" :D. You're gonna love it!!

Cheers,
Bob
 
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My airport is around 7000' MSL. To the west are the Rockies. My mindset is to fly at a minimum of 10,000' MSL. One reason is that in this area I need that just to have a reasonable height above the ground. Another is to be in airspace that has far fewer GA aircraft.

Going west I am in the 12,500' to 16,500' range depending upon the trip.

I don't have a set altitude versus en route flight time decision making tool. Going west, mountains are the big factor. Going east, I often stay at 11,500'. That is high enough to be above traffic and yet not use oxygen (I live at 6800' so this may not work for sea level dwellers).
 
Altitude flying

DakotaHawk said:
So...

What is the greatest benefit to flying higher? Is it improved economy, less traffic, better ground speed?

What is the trade-off? Is it less control feel, length of each leg, or something else?

What is the break even point for, say, a climb to 10k? Would you climb to 10k for a one-hour cross country? A two-hour cross country? Three?
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Usually on a trip of at least 100 miles I fly at either 11,500' or 12,500', for a density altitude in the 14,000' - 15,000' range. It keeps me out of the turbulence down lower and the traffic is minimal. I get my best economy at these altitudes, usually burning 5.6-5.7 gph at 198 mph TAS for about 35 mpg during cruise. Flying at a lower altitude, for me, lowers the mpg. Unless there is a big wind advantage lower I stay highl The plane handles about the same, and even at this altitude my ROC is about 500 fpm. 'Course I have a NACA-designed Liquid Overboard Dispensing System which allows me to make 5-6 hr flights and not have to worry about that last cup of coffee before the flight and to keep a bottle of Gatorade and snacks beside me.
 
Hmmmmm

Liquid overboard dispensing system, or LODS. I like it. Is there, um, design documentation? (Seriously, in that designing this wrong defeats the purpose in a very unpleasant manner, lol)

Rick 90432
 
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LODS

rjcthree said:
Liquid overboard dispensing system, or LODS. I like it. Is there, um, design documentation? (Seriously, in that designing this wrong defeats the purpose in a very unpleasant manner, lol)

Rick 90432
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You're so right! When my friend put one on his plane, he only used a piece of 3/8" plastic tubing and just ran it slightly out of the bottom of the plane cut off at an angle to the rear. His brother prepared a jug of water that was to have a little bit of red coloring, but his brother added the whole bottle! Wow!, was the bottom of that plane red. Take a piece of 3/8" foam 4" W x 3" L, poke a 5" piece of 1/4" aluminium tubing through the 3/8" edge about 1.25" back from what will be the leading edge on the 4" side, form it into a smooth streamline airfoil shape with a 4" chord and 3" span, then cut it starting at the top forward edge of the LE to a point 2" down on the TE. Then make a parallel cut from the LE 1" down from the top to a point at the bottom of the TE. That should give a 30 deg swept airfoil with a 4" chord and 7/8" span. Pull the tube back and cut it at an angles so that it's flush on the bottom. Cover the foam with fiberglass-epoxy, and attach to the bottom of the plane with the tube sticking up through about 2". By having the edge of the tube 7/8" out into the airstream, the liquid will all go out into the airstream and nothing will get on the bottom of the plane! Now make a receptacle to match the fluid nozzle dimensions and connect it to the LODS with plastic tubing. Feel justifiably proud that you will be contributing to the greening of your country!
 
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