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How High?

nigelspeedy

Well Known Member
Today I set out to find out how high my 8 would go. I did some level accel's from 2 to 18k to determine the climb performance and then came up with a climb schedule to do a ceiling climb. Taking off out of Mojave at 1600 lbs I used 120 KIAS to 10,000', 100 KIAS to 15,000', 90 KIAS to 20,000', 80 KIAS to 25,000', 75 KIAS to 27,000' then 70 KIAS which got me up to 28,000'.

Some observations. It's bloody cold up high. Aluminum is a great conductor of heat. Pens and iPhones don't work very well when cold. The RV-8 cabin heater is no match for -40C. The Dynon Skyview system stops reporting OAT below -32C.

The flight was spoiled by being passed as traffic to a jet climbing out of China Lake as "a very slow moving RV at 280". Granted 38 knots ground speed is a little on the slow side for an RV.

These planes really need a blower or turbo to increase the shabby high alt performance.


547702ba-95c1-4d2e-a1c1-bcba3ce81e9c_zpsibkbsam3.png" border="0" alt="RV-8 Ceiling photo 547702ba-95c1-4d2e-a1c1-bcba3ce81e9c_zpsibkbsam3.png
 
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This is great! A very slow moving RV. Sounds like we need a turbine upgrade (and pressurized/heated cabins).

Or, as some wise aviator said, " fly near the middle of the air; stay away from the edges" You're too close with your bird. Icarus, you know.

(way too cool, BTW!!)
 
Thats super cool. Inquiring minds want (need?) to know: How exactly does one successfully make the request of ATC to get cleared to do that, slow and in the flight levels? Block from surface to 30,000? :)

Also, I hope maybe you had heated seats at least. How long were you up there in that cold?
 
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T...The flight was spoiled by being passed as traffic to a jet climbing out of China Lake as "a very slow moving RV at 280". Granted 38 knots ground speed is a little on the slow side for an RV....

Thanks for the report on a very nice flight. Don't feel bad about the 38 knots. I made a flight in a Schweizer 1-26 at FL300 where my ground speed was in the range of + or - 20 knots. It was cold for me with the fabric and steel tube and aluminum but maybe not quite so bad since the lower speed limited heat transfer.
 
I think that's the highest I have ever heard or read about for a normally-aspirated two-seat RV. I've been to FL250, but as you said, it gets dang cold, and I started to worry about magneto arc trackign and other stuff not designed for that environment.

Nice envelope expansion!
 
Clearance how?

I work at NTPS and we have a good relationship with the controlling agency for the Isabella MOA and they routinely allow us to operate aircraft VFR up to 290 and above. So I just put myself on the flying schedule and flew to work and used a work call sign. I actually asked for 300 in a fit of optimism and they approved that once airborne. You could just file IFR though. Be prepared for a long climb, it took me 40 minutes to get from 2700' to 28000'. I spent about 5 minutes up there messing around with different mixture settings and airspeeds but the novelty wore off pretty quick. One of those things you do once to say you did, but I think 18000 is a more practical ceiling (the engine actually makes enough power that the heater works & you can use a cannula instead of a mask) unless there was a scorching tailwind that you just couldn't pass up. I wore a pulse oximeter and lowest I saw was 92% O2 Sat. Have fun exploring.
 
Always wanted to try that in my 9, but don't have a mask. 18k (with cannula) is easy in the 9, still climbing at ~700 fpm.

Greg
 
Good to know

We used to marvel at Brue and the Exxon Tiger down in Houston. These reports are good to know for those of us that like to bump class A airspace from time to time. Good job, keep it coming. Yours as always, R.E.A. III #80888
 
I don't wish to rain on your parade but I personally don't think this is a very sensible thing to do. OK, once to get a record but certainly not routinely.

- winds/turbulence aloft could easily cause structural issues not to mention literally going backwards

- "The Bends" are possible above 18,000'

- O2 failure? How many have done hypoxia training? It's insidious and difficult for someone trained to pick up let alone someone untrained. How long is it going to take to get down from that altitude to somewhere where you can breath? At 28,000', your period of useful consciousness is in the order of 2 minutes......

Just a few thoughts for anyone wishing to repeat this.
 
Awesome trip report! This is good exp-AB stuff.

I've wondered just how high I could get my -8. Thought low/mid 20-s would be realistic. You've beat that handily.

Put a NOx tank in and see if you can catch Bruce Bohannon's record. Probably ought to get a pressure suit though. Shouldn't be too hard to find one to borrow working at the NTPS...

Paul330, check Nigel's profile. I think he's good to go.
 
I did that once in a Cessna 182. Half fuel and pilot only. Made it to 21,400. Yes, cold; and the aircraft felt really wobbly. Slow, very shallow turns. Took a long time from about FL190 to FL214. Heard a transmission from military jet reporting ETA at my location; so headed down as fast as possible.
 
Canopy?

Cool!!! I was wondering about the canopy shrinkage at the temp? Is it riveted or sickaflexed ? Any cracks around rivets or separation from the bonding?
They know about the shrinkage...don't they?
 
Monkey has a point. At those altitudes, what kinds of structural things are happening? Canopy breakage, possible freezing of flight controls?
Something I didnt think of, but I'm sure others have. I dont plan on flying that high, but its also good to know that it has been done.
I'll talk to my mentor, Lee Logan about it.
Tom
 
Dangers of high flight.

Paul330,

You make some very good points and they are well worth brining up.

I thought quite a lot about this before I did it, it wasn't just a spur of the moment activity. Risk management is about making things as safe as reasonably practicable, ensuring the risk is worth the reward, and within your personal tolerance level. I only planned on doing this once which limited the exposure to the hazards. I also accept that a lot of people will not want to do this.

You can pick your day and hence the weather, winds at altitude and turbulence. On my flight it was glassy smooth above 8k but as you allude to mountain wave or jet stream could easily create turbulence that could exceed the performance capability and structural limits of an RV.

You need to be careful with your IAS on descent if you don't want to exceed the Vans recommended TAS limit. Easy if you have an EFIS that displays it real time, but a prepared IAS v Alt VNE limit chart would be wise if you don't have that luxury.

I don't think there is any great risk to a negative groundspeed if your indicated airspeed is positive, but I am a helicopter guy by trade so I think backwards is a normal mode of flight. Could certainly be inconvenient if you were constrained by airspace though.

So far the canopy has help up. It was mostly riveted on and Sika flex used in spots to fill gaps.

You are right about the risk of DCI or the bends, in some places they won't let you fly above 18k unpressurised without pre-breathing 100% for sometime. I have had the luxury of doing several chamber runs over the years and am familiar with my personal hypoxia symptoms and they are quite consistent. The FAA runs courses that you can do for free and if you haven't had the chance to experience hypoxia I heartily recommend you get some training. I made sure my O2 system was serviced and took a spare controller. I wore a pulse oxy meter the whole time and checked it regularly. I also wore a parachute.

Still. there is no denying you are left with some failure modes that have likely catastrophic consequences and some probability.

Cheers
Nige
 
Someone Will Always See the Dark Side

For all you naysayers:
Speedi is a test pilot instructor at NTPS, is very familiar with the airspace and terrain, REALLY understands what his airplane is telling him, is very familiar with high altitude physiology, understands how to work well within R-2508 and with the procedures used by Joshua Approach controllers, and like all of us who regularly fly over the Southern Sierra, probably has well thought out Plans B, C, ....when things start to go south.

Attaboy Speedi - keep expanding the envelope and our knowledge of it. Although after spending 10+ hours in temps in the low twenties on a recent flight to PA from IYK, I have no desire to fly in air any colder!
 
Nigel,

Do you want to try that with my O-360 powered -9?

With the Ronz airfoil and longer wing, I'll bet you could go a good bit higher.

Couple that with the EICommander to keep track of the ignition, you should be good to go.
 
Speed

Nigel, your high altitude run is very cool in my book. thanks for the report. I have seen your dyno charts, I was wondering what your RV-8 does wide open?
 
Very cool Nigel!

In May of 2008, John Brick flew his RV-4 with an IO-360B1B to FL280 (28,250' MSL). I remember him talking about how cold it was, if I recall correctly he said it was -60F. :eek:
 
Nigel,

Do you want to try that with my O-360 powered -9?

With the Ronz airfoil and longer wing, I'll bet you could go a good bit higher.

Couple that with the EICommander to keep track of the ignition, you should be good to go.

That just what I was thinking - with my IO-360, EI and CS prop this should be achievable. Proper attention to risk management is a must, however. Physiological factors are a prime attention-getter.
 
I too think this was a very interesting and cool thing to do.

I'm wondering why the airspeed was so low. Was it because all the thrust is being used to keep the aircraft at altitude, kind of like a helicopter?

Were you right on the verge of a stall?

Just curious.
 
I too think this was a very interesting and cool thing to do.

I'm wondering why the airspeed was so low. Was it because all the thrust is being used to keep the aircraft at altitude, kind of like a helicopter?

Were you right on the verge of a stall?

Just curious.

I think you are right, look at his AOA/lift reserve on the EFIS display...No green at all

I'm also wondering if overspeed of the engine is possible? because the C.S. prop has to run out of coarse pitch at some point(not a lot of air molecules to push against). Or maybe it doesnt matter because the engine is limited to approx 33% power. Any engine parameter screen photos Nigel?
 
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The flight-aware track shows climb rate was variable near 100 fpm there for the last 1000 feet, the engine can't make power, the prop can't make thrust, the wing can't make lift, this was maxed out.
 
Absolute ceiling

... that place I've never visited where Vx, Vy and Vs1 all come together on the airspeed indicator. Also known as coffin corner for trans-sonic-capable aircraft, but not so much for RV's.

I bet the air is fresh and bracing up there. :)
 
28000 plus!

I thought coffin corner was where stall and limiting mach intersected. The mach number for this flight wasn't very high, but I have no idea if the RV-8 even has a limiting mach. Anybody?
 
0.172 Mach

Not sure where the RV-8 runs into Mach buffet but probably higher than Mach 0.172.

When slowed to 55 KIAS the stall warning started to come on and at 65 KIAS it was descending, so a narrow workable range. The plane flew just fine though. If you are happy with slow flight at sea level you would not be surprised by the handling when flying slow at altitude.

I set the prop once when I started the climb and it didn't change by more than 10 RPM on the way up or down.

At 20,000' the fuel pressure started to drop so I put the boost pump on until I was below that altitude again.

Cheers

Nige
 
Ok please educate Me the dum dum

Mach limit? What the.....? Please explain.

And Ya, how do you stay aloft if the IAS is 38? What was the TAS again?

As Slider said, "Gutsiest move I ever saw, man!" And may I point out that you got the cooolest last name ever! If that's really your last name😊
For those who don't know who Slider is, shame on you!

Forget this Star Wars business, I'm camping out for 12 days when Top Gun 2 comes out!
 
Into thin air...

Some observations. It's bloody cold up high. Aluminum is a great conductor of heat. Pens and iPhones don't work very well when cold. The RV-8 cabin heater is no match for -40C. The Dynon Skyview system stops reporting OAT below -32C.

The flight was spoiled by being passed as traffic to a jet climbing out of China Lake as "a very slow moving RV at 280". Granted 38 knots ground speed is a little on the slow side for an RV.

These planes really need a blower or turbo to increase the shabby high alt performance.

Nigel,
Many moons ago I nursed my very lightweight, carbureted 150HP "wood propped wonder" RV4 The Bandit to FL200 (no heater) and realized your realization 20 years hence! With water bottle frozen solid and chattering teeth forcing a retreat to thicker air I descended post haste. From many altitude chamber briefings and physiological systems classes, venturing above FL250 is inviting trouble without proper training or equipment. Nuff said.
Like you I have spent many hours above FL400 and Six Bills over the ground, fat dumb and happy in a modern pressurized Jet. However, I always marveled at those who went before.

Wiley Post zoomed the Winnie Mae Lockheed Vega to 51,000' in the early 30's and LTC Mario Pezzi somehow coaxed a blower equipped Caproni Biplane to 56,000' in 1938! Joe Kittenger jumping out of a balloon from 100K over 50 years ago....the list goes on.
I've often wondered what it would take to break Pezzi's record. Easy answer, lots of money. Bruce's Exxon Tiger basically a souped up RV4/HR1 topped out at just above FL400 with a supercharged fire breathing IO-540. Personally I think the way to attack it (RV wise) would be a very light weight RV12 with a Rotax 914, turbo Revmaster or blower equipped RV9 with a donned pressure suit and an aux heater.

Over the years several RV guys have experimented with blowers and turbos. I even experimented with a 12V electric leaf blower on my RV4, with not much success.
But I digress.

It could be done...:)

V/R
Smokey
 
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Nigel's great flight seems to be aimed at determining what the aircraft is capable of with no atmospheric help, but when it comes to records I always wonder why pilots don't take advantage of free help.

I noticed today that the Perlan II glider took up residence over the way from Paul and Louise's and others spots. So this is an efficient airframe with no engine, that is expected to be able to reach an altitude of around 90,000 feet. Yes, with no engine they expect to be able to fly higher than any air breathing aircraft has been able to go.

As noted above, I have been to 30,000 feet with no engine in quite a crude glider with low performance. That makes me feel sure that an air breathing engine powered airplane should be able to gain at least another 10,000 feet or so by using atmospheric lift.

So, while wondering why this free aid is not used, other than the increased trouble of waiting for the right conditions in the right area, I also wonder how much benefit there would be. The glider generally has more efficient aerodynamics but the powered airplane has the help of the engine that becomes increasingly less helpful with altitude. There is a crossover point that I am not near smart enough to figure out.
 
After flying the -9 for a few years, I started to wonder what Bruce B. could do with the Tiger, if fitted with -9 wings.

For those of you who have not had a chance to fly the -9(A), the wing is simply amazing!
 
Thanks for your explanation, Nigel. I can see you carefully thought it through and have had the necessary experience/training to do, what I assume, was a test flight "to see if it was there" rather than advocating it as a way to get from A to B.

The only problem is that other less capable people may be tempted. A lot of questions that have come up show that high altitude flight is not well understood by some.

May I just add a word of caution - "Don't try this at home...."
 
Mach limit? What the.....? Please explain.

Many transport catagory aircraft are not designed for any supersonic airflow, e.g., if the air over the wing goes supersonic shock waves may be set up preventing the ailerons from working properly, the center of lift may suddenly change, etc. So there is a "red line" not to be exceeded. Since the airspeed over the wing is faster than the airplane's speed, this redline has to be less than Mach 1, often like Mach 0.85. This is a True airspeed, and is the "Mach Limit".
At the same time, stall speed depends on indicated airspeed. If you are flying at (true) speed Mach 0.84 and climbing, the indicated airspeed eventually gets so low that it approaches stall speed. This is the "coffin corner"; any slower and you stall (bad), any faster and you exceed Mach 1 on top of the wing (bad).
 
Did you check your avionics before and after?
There are capacitors where absolutely do not like these altitudes!

Cheers Yves
 
Some charts from the climb

Dist%20to%20Climb_zps9eprivfm.png
[/URL][/IMG]

Fuel%20to%20Climb_zpsm2vg8ea7.png
[/URL][/IMG]

ROC_zpseuqs2uns.png
[/URL][/IMG]

Time%20to%20Climb_zpskf1o2ga4.png
[/URL][/IMG]

Cheers
Nigel
 
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THANKS - SOME QUESTIONS

G'day Nigel,

well planned, flown & reported. Great data - thanks.

Questions:

Why 2500 RPM ?

Was 1200F a target EGT for the climb ?

What was your logic for your varying climb speeds, eg: Vz, then Vy to Vx, or ?

Regards.
 
Answers for Bob

G'day Bob.

I used 2500 RPM for a few reasons. The take off maximum is 2700 RPM & the max continuous for the prop is 2600 RPM. It was balanced at 2500 RPM and is nice and smooth there. I guess I could have used 2600 RPM for a little more power but I normally use 2500 RPM so the data is representative of what I do on a daily basis.

I normally lean the engine as I climb. At sea level with full throttle, 2500 RPM and mixture full forward I see 1200F EGT (as an average), so as I climb I use this as my target EGT. So about every 1000' or so I lean a little to keep the EGT's about 1200F. So as I climb fuel flow goes down and EGT stays the same.

At Vy (100 KIAS) the aircraft is about 15 degrees nose high so forward field of view is not very good. At 120 KIAS I can see the horizon over the nose, spotting traffic is easier, cylinders stay cooler, and I still get comfortably over 1000 fpm to 10k. Above 10k the climb rate has dropped off such that climbing at Vy (100 KIAS) I still have good forward field of view. As you get higher Vx, Vy & Vh collapse to the same value so the choice for speed is made for you. Unless time is of the essence climbing at the speed that gives the best product of ROC and TAS seems more practical. One of the Boeing flight test guys wrote a good paper on the subject. If you search for "Introducing Vz" by Norman E Howell you should find it online. These aircraft have nice flat performance curves so the penalty for being a little fast or slow is pretty low, you can pick nice round numbers that are easy to remember for your climb schedule without fear.

Cheers
Nice
 
Speedy, what kind of engine do you have in your RV-8? I'm just curious if these charts apply to my 180HP Lyc?

Nice experiment!
 
Paul330,

You make some very good points and they are well worth brining up.

I thought quite a lot about this before I did it, it wasn't just a spur of the moment activity. Risk management is about making things as safe as reasonably practicable, ensuring the risk is worth the reward, and within your personal tolerance level. I only planned on doing this once which limited the exposure to the hazards. I also accept that a lot of people will not want to do this.

You can pick your day and hence the weather, winds at altitude and turbulence. On my flight it was glassy smooth above 8k but as you allude to mountain wave or jet stream could easily create turbulence that could exceed the performance capability and structural limits of an RV.

You need to be careful with your IAS on descent if you don't want to exceed the Vans recommended TAS limit. Easy if you have an EFIS that displays it real time, but a prepared IAS v Alt VNE limit chart would be wise if you don't have that luxury.

I don't think there is any great risk to a negative groundspeed if your indicated airspeed is positive, but I am a helicopter guy by trade so I think backwards is a normal mode of flight. Could certainly be inconvenient if you were constrained by airspace though.

So far the canopy has help up. It was mostly riveted on and Sika flex used in spots to fill gaps.

You are right about the risk of DCI or the bends, in some places they won't let you fly above 18k unpressurised without pre-breathing 100% for sometime. I have had the luxury of doing several chamber runs over the years and am familiar with my personal hypoxia symptoms and they are quite consistent. The FAA runs courses that you can do for free and if you haven't had the chance to experience hypoxia I heartily recommend you get some training. I made sure my O2 system was serviced and took a spare controller. I wore a pulse oxy meter the whole time and checked it regularly. I also wore a parachute.

Still. there is no denying you are left with some failure modes that have likely catastrophic consequences and some probability.

Cheers
Nige

Most of my flying career was above 28,000'. I can not imagine being there on a regular basis in a RV. There are days you wish you were not there in equipment designed to be there.

You obviously planned this mission well and it worked out. But as you mention there is risk doing it and you knew it.

Interesting mission report, congrats on it's success. :)

(Makes one appreciate the guys who flew in WWII. It was just as cold then and the missions were long.)
 
G'day Bob.

I used 2500 RPM for a few reasons. The take off maximum is 2700 RPM & the max continuous for the prop is 2600 RPM. It was balanced at 2500 RPM and is nice and smooth there. I guess I could have used 2600 RPM for a little more power but I normally use 2500 RPM so the data is representative of what I do on a daily basis.

I normally lean the engine as I climb. At sea level with full throttle, 2500 RPM and mixture full forward I see 1200F EGT (as an average), so as I climb I use this as my target EGT. So about every 1000' or so I lean a little to keep the EGT's about 1200F. So as I climb fuel flow goes down and EGT stays the same.

At Vy (100 KIAS) the aircraft is about 15 degrees nose high so forward field of view is not very good. At 120 KIAS I can see the horizon over the nose, spotting traffic is easier, cylinders stay cooler, and I still get comfortably over 1000 fpm to 10k. Above 10k the climb rate has dropped off such that climbing at Vy (100 KIAS) I still have good forward field of view. As you get higher Vx, Vy & Vh collapse to the same value so the choice for speed is made for you. Unless time is of the essence climbing at the speed that gives the best product of ROC and TAS seems more practical. One of the Boeing flight test guys wrote a good paper on the subject. If you search for "Introducing Vz" by Norman E Howell you should find it online. These aircraft have nice flat performance curves so the penalty for being a little fast or slow is pretty low, you can pick nice round numbers that are easy to remember for your climb schedule without fear.

Cheers
Nice

Target EGT method is sound. :) Just a bit of explanation for others reading, when you reduce RPM the peak pressure moves to a lessor ThetaPP, or closer to TDC. In doing so the peak pressure becomes higher, and due to a greater DeltaP to atmosphere, and more expansion of the gas, the EGT is a lower value. Not to mention there are fewer exhausts per second on the probe. SO 1200 sounds a fair number.

Doing this target EGT all the way up ends up being about 75 or so ROP once into the FL's which is what you want up there for the greatest power you can achieve.

Norman's publication on Vz is an excellent read and I suggest everyone reads it. In simple terms most RV's are best climbed at 115-125 (depending on model) for all the reasons mentioned above by Nigel.

FL170 is the most I have used for the -10, and 130-150 is where I normally hang out on long trips where weather and or winds make it more desirable up there.
 
THANK YOU

G'day Nigel,

I first heard about Vz about 2 years ago and was sent part of the Howell paper. Following your advice I found and read the complete paper - good read, and good revision.

I was using a cruise climb of about Carson?s Speed of 105KIAS for our stock RV-7 (Aerosport ECI IO-360 M1B, 8.5:1, 180HP, PMags, Hartzell CS BA - 2700 for take-off, then 2600RPM max continuous), but now usually just use 120KIAS to better manage engine oil temps, particularly during summer after a hot start and second climb. CHTs good in climb and cruise. Oil temps good in cruise.

After much reading and discussion (particularly with David Brown), also I now use the target EGT climb method - No 1 cylinder 730C (1346F) and cruise just LOP at about 66%, 30 litres/hr (8 USG/hr), 100LL.

Again, thank you for posting your data, and for your answers. I am glad for confirmation that at least some of my practices are shared within the test flying profession.

Best regards,
 
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