How High?

[YvesCH]

Did you check your avionics before and after?
There are capacitors where absolutely do not like these altitudes!

Cheers Yves

[nigelspeedy]

[IMG][/IMG]

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Cheers
Nigel

[Ironflight]

Nice smooth data plots Nigel - the mark of a professional!

Paul

[Bob Redman]

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.

[KRviator]

Originally Posted by control

Still over 1000fpm @ 16000

234HP in an RV-8 will do that!

Same donk in a -9 would probably get well over FL300!

[nigelspeedy]

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

[Stroh21]

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!

[David-aviator]

Originally Posted by nigelspeedy

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.)

[RV10inOz]

Originally Posted by nigelspeedy

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.

[Bob Redman]

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,