Flatlanders Up At 14,000 - Learned A Lot

Sinistar

Sinistar

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Brad
Yesterday I met up with @WannFly and we did a trial run to get more prepared for a potential trip out to Wyoming this coming fall. It was great having another pilot along for this test as the highest I had been before was 11,000 and this upcoming flight might need higher and thus 02 as well. All data is for a 1972 Cessna 182P (stock 230HP).

We took off from 1450msl at around 75F and DA=2600. The plane was loaded similar to what we will fly. The takeoff roll was nice at about 1000ft with some headwind. There was a very sparse layer of FEW @5500 so no problem going VFR up around/over those.

For this one I flew at 85mph which is recommend for best rate of climb above 10,000. From the ground we were climbing around 1000fpm and held 800fpm to about 7,500. Then the climb rate started dropping to around 550fpm and would continue down to about 0fpm at 14,000. We started with manifold pressure of 23" and was at 9" when we leveled off - didn't expect it to be so low. So we stopped there...but for more than one reason.

Temperatures were a bit weird in that they remained the same from 6,000ft to 11,000ft so it was warmer than the standard lapse rate. The field altimeter was 30.10

This was also the first time I have worked out the engine HP loss based on our altitudes. At 14,000msl we were at DA=15,200ft. The 230HP engine will put out only 125HP at that altitude...wow!!!! In hindsight, its funny to think a fatty Skylane with a fatty pilot can even fly at 125HP.

But we both agreed that most important lesson learned was O2 management.

We had a single oximeter and for this test and probably should have each had our own. It displays heart rate and O2 and once up at the higher altitudes it was easy to mistake one for the other. Later I figured out a different display option I should have used.

We were both showing in the low 90's around DA=10,900. Then after that it started falling off quicker than we had expected. We started seeing numbers in the low 80's (eg 82 & 83) when at DA=12,100ft....DA=15,212ft.

What was more surprising was how quickly those numbers would drop after taking 3 or 4 hits off the 02 cans. I thought a good 3 or 4 hits might last like 10 minutes but I think it was maybe lasting 3-4 minutes. At one point I could start to tell, feeling a bit weak, but he was throwing me a few random math problems and says I didn't screw up any. Now I know what it feels like. I am also a scuba diver. It was not like being narc'd - that is a bit more euphoric. This was a bit more "low energy" which of course makes sense.

In either case we decided since we were using more 02 than we initially guessed that we should head back down and get some fresh air. We spiraled back down which also takes a while. I was in a bit of hurry as I still had one flight left after this. So our ears weren't happy with that descent. On the ground we chatted for about 15 minutes, made sure neither of us were feeling weird and were both still just as stupid and then he drove home and I flew home.

I believe the 182 has a service ceiling of 17,700. Had our day been about 20deg cooler and had the temperature lapse rate been more normal I think we could have reached a DA=17,000 or just a bit less. So fairly close to book numbers.

Thanks for riding with @WannFly! Hopefully your annual wraps up soon so you can get back to flying your baby!
 
You actually got to the absolute ceiling (vs=0), not the service ceiling. You were at that when you were doing 100fpm at best climb speed.

Sent from my Pixel 2 XL using Tapatalk
 
Kinda interesting isn’t it?

I won’t stay up there if below 90 on a pulse ox. That’s getting too low.

I’m surprised one or the other of you didn’t get a headache from that. :

Did you find it interesting how sloppy the controls got up there, flying fairly slow?

You can see why the time to climb isn’t really worth it unless there’s a ripping tailwind aloft. Then it’s worth pulling out the O2 and climbing. It’s just too slow to bother with most of the time.

Seconded that you found your absolute ceiling and it arrived long before the published service ceiling.

Did you continue to lean the engine as you went up? I assume you did and have at least a single point EGT. If it’s the Continental it’ll get sluggish if you don’t keep aggressively leaning.

Once you’re below 65% power If temps stay in line you can lean for peak. It’s not making enough power to get too hot, and that’s the best power you’re going to get up there usually. You can hear it in the prop governor as you dial it in. It’ll rev a tiny bit if you’re going the right way and then the prop will put it back.

Also up there remember there’s no actual limit on RPM to stay in the green arc on the Continental. You can leave it at redline. That’ll get you about 100-200 more ft/min when it starts to run out. It won’t make it much above where you were at without being maxed out.

It’s weird to feel like you’re flogging it hard but you truly aren’t. As you saw by your MP gauge. The high RPM maybe means more internal cycles on the engine but it isn’t working very hard.

But definitely consider not below 90 on O2. That’d get a nurse’s attention on a hospital floor. LOL.
 
frfly172 said:
I would recommend, that if your going to make that flight again, you have one pilot on o2 just in case .
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Got It!

Actually we were both using 02 but just using cans. As you can tell we didn't care for the rate we were dragging off the cans and bailed once we leveled off at 14K. I think what made it a PITA was sharing the oximeter.

No way I would have done that single pilot or pilot + non-pilot passenger.

There are some great threads here on O2 systems (purchased or DIY). I have already been sold on a larger delivery system vs the cans (@WannFly did you hear that). With no AP and having to drag every 3...5 minutes it just seems like a hassle and definitely not the place or time to introduce that type of hassle. Sure if it is a 20 minute popup from 10K to 13K and back down again I could see using the cans. Otherwise seems like a delivery system would be much better.

I remember as we prepared we planned on just having them laying on the seat behind us because we didn't think we'd need them that often. Around 13K it became obvious that having them in the backseat and reaching back was definitely not preferred. I ended up just laying the can under my left elbow on the arm rest. I have a small plastic console we probably should have used.
 
mwagg737 said:
You actually got to the absolute ceiling (vs=0), not the service ceiling. You were at that when you were doing 100fpm at best climb speed.

Sent from my Pixel 2 XL using Tapatalk
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Thanks for clarifying....duh on my part. From that test where we were around 100fpm was probably DA=14000 or so. So then definitely not book numbers.

This brings up a more general question. If we stick to normally aspirated single engine piston planes and lets go more specific with 180/182/Dakota/Pathfinder/etc or basically all the 230HP or 235HP non-turbo planes. Can any of those go much higher than we did? No matter what they will be like a 125HP plane up there right? So how often are people in those classes of planes flying over 10K mountains at say 13K?

I would think this would make the SR20 at 200HP even more difficult to climb to DA=15,000. Its lighter and more aerodynamic yet would have less HP. Or is there something to do with Fuel Injection vs carb'd?

I always thought a 270HP engine in the Skylane would be a sweet spot. We would have been a 165HP plane at DA=152000 vs 125HP. in theory we would still be climbing around 300fpm or a bit more.
 
Sinistar said:
This brings up a more general question. If we stick to normally aspirated single engine piston planes and lets go more specific with 180/182/Dakota/Pathfinder/etc or basically all the 230HP or 235HP non-turbo planes. Can any of those go much higher than we did? No matter what they will be like a 125HP plane up there right? So how often are people in those classes of planes flying over 10K mountains at say 13K?
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They can usually go a little higher but it’s a slow process.

Usually I go through the mountain passes and am not trying to clear the tops of 14’ers.

13,500 is usually plenty for that with proper training for escape routes and mechanical turbulence. And I’ll get back down below the need for O2 relatively quickly.

No need to loiter up there, the Continental Divide just isn’t that wide in most spots where you’d cross it.
 
denverpilot said:
Kinda interesting isn’t it?

I won’t stay up there if below 90 on a pulse ox. That’s getting too low.

I’m surprised one or the other of you didn’t get a headache from that. :

Did you find it interesting how sloppy the controls got up there, flying fairly slow?

You can see why the time to climb isn’t really worth it unless there’s a ripping tailwind aloft. Then it’s worth pulling out the O2 and climbing. It’s just too slow to bother with most of the time.

Seconded that you found your absolute ceiling and it arrived long before the published service ceiling.

Did you continue to lean the engine as you went up? I assume you did and have at least a single point EGT. If it’s the Continental it’ll get sluggish if you don’t keep aggressively leaning.

Once you’re below 65% power If temps stay in line you can lean for peak. It’s not making enough power to get too hot, and that’s the best power you’re going to get up there usually. You can hear it in the prop governor as you dial it in. It’ll rev a tiny bit if you’re going the right way and then the prop will put it back.

Also up there remember there’s no actual limit on RPM to stay in the green arc on the Continental. You can leave it at redline. That’ll get you about 100-200 more ft/min when it starts to run out. It won’t make it much above where you were at without being maxed out.

It’s weird to feel like you’re flogging it hard but you truly aren’t. As you saw by your MP gauge. The high RPM maybe means more internal cycles on the engine but it isn’t working very hard.

But definitely consider not below 90 on O2. That’d get a nurse’s attention on a hospital floor. LOL.
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Thanks for offering insight Nate! You live up in the mountains and are in this all the time.

Re:Headache. I figured for sure I would get a headache. But I didn't. I also figured I would be really wiped out but wasn't. But it was very obvious when O2 got low in the lower 80's. Just started feeling tired. @WannFly can tell you if was getting silly! We both took that 15minute break on the ground before operating more machinery. But I think his "Black Ram" could probably drive him home with that monster console/computer in the middle :)

I was leaning, not often and probably not aggressively. I sticked the tanks before and after (not accurate) and showed about 10gal used for almost an hour of flight of which 2/3 was the climb and level off. So I definitely wasn't running rich. I have even gotten more comfortable taking off slightly leaned when DA is up a bit so I probably tookoff with the mixture out about 1" and then pulled it back another 1" for the first part of the climb. And maybe another 1/2" for the rest of the climb. With no engine monitor I can only do the stumble and back in approach.

I guess I didn't have the prop all the way in. When I get about 700agl after takeoff I bring it back into the green arch (about 150rpm or so). I left it there for the entire climb.

So maybe a few takeaways is that I could have probably leaned a bit more and I could have brought the prop all the way back in.

You know, since I was climbing at 85mph it didn't feel that sluggish. When I turned 180 it was the classic slow flight turn. Standard turn rate, light nudge of the rudder pedal and feels like spinning on a dime. When I did a test flight to 11K I was pitched at 75mph for some of it. That felt a lot more like slow flight (no flaps).
 
Actuall, neither Nate nor I live in the mountains, but on the flatlands. But our flatlands are 5k-6k msl.
Which is probably cruise alt for many on POA. With DA in the summer, our ‘ground’ can start at 8k. As Nate pointed out, we don’t fly over the tops but thru passes. Altho I’ve had my cherokee 180 up to 15.5k, my usual top is 12.5-13.5k for the passes.
 
Kudos to @Sinistar for not getting a headache with me in the right seat and surprisingly i didnt get any headache either. though we were both taking the O2 shots the min we saw O2 getting to 90 or below. i did feel stupid, but i feel that on the ground anyway, so nothing different up there. i have taken a 172 many moons ago to 14.5 with a CFI and didnt feel anything funny either, didnt measure O2 so no idea what the levels were and we were up there may be 10 -15 mins.

this was a great learning experience and i am glad we didnt find this out first time while flying over big rocks. for flatlanders this was an invaluable experience and was an eye opening. it is evident how people get into trouble and we read in the NTSB reports of some dude who tried to get off the runway and climb just by will power on a hot day at a 7k feet airport with a DA of 9-10K

  • I know my Archer will get sluggish at that alt if i can climb there at all, didnt expect that with the 182. there was a point were i saw -50 FPM climb, we were close to 14k at that point
  • we knew O2 will be a problem, we didnt know how big of a problem it will be, i believe we were both at 90 right after we left 11k, down at low 80s every 100 feet or so, which were taking about 4 mins to climb
  • We used lot more O2 than we thought we would need, even during decent Brad was taking the O2 shots till about 9k i believe, thanks to him for doing that, it would have sucked to have him passed out and get my first HP landing without endorsement ... lol
  • Keeping the O2 handy, measuring the levels and taking shots as and when required resulted in more workload than i had anticipated.

out current plans is to fly that way week of Sep 15 (or may even be a week after, dont know yet), subject to WX etc. the planned route at WY will take us over a pass at 9500 MSL, we would like to keep 3000 ft difference between us and the rocks, thats puts us at 12.5. i have been calculating the DA over the pass every day and i havent seen anything below 14.5 yet, even in the AM. at that point with our weight and planned fuel, we will be at less than 100 ft per min climp and will not be able to outclimb the smallest and weakest of downdrafts. our initial planned route was

day 1
KFAR / KGYL - KPIR - KRIW

Day 2

KRIW - KJAC over the Togwotee pass

and then we have a bunch of other legs planned which right now seems like a pipe dream


meet up can surely be a possibility, may be we should start another thread on it Brad @Sinistar .
 
Remember that temps drop when you get higher. Year ago,June, I went from Denver to Alamosa by way of PUB then Mosca Pass. Took the pass at 13.5 altho I planned for 12.5. But the cherokee just kept climbing. I wasn’t expecting the cold, so I threw the flight bag down on the pax floor to block the cold air coming in the floor vents. At this timestamp, noon Aug 23, Monarch Pass is 53 deg at physical alt of 12k.
 
murphey said:
Remember that temps drop when you get higher. Year ago,June, I went from Denver to Alamosa by way of PUB then Mosca Pass. Took the pass at 13.5 altho I planned for 12.5. But the cherokee just kept climbing. I wasn’t expecting the cold, so I threw the flight bag down on the pax floor to block the cold air coming in the floor vents. At this timestamp, noon Aug 23, Monarch Pass is 53 deg at physical alt of 12k.
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yah, i have been running the numbers based on wind aloft data and temp, but again thats not real time actual temps...

the other route is going south via Rock Springs , which we should probably look at as a backup. i know nothing about mountain flying other than reading a couple of books so being ultra-conservative (read wimpy)
 
HP is torque x RPM (divided by a constant). The rule of thumb is a 3% loss for every 1000ft of altitude gained.

Fuel injection vs carb isn’t going to provide any better performance at altitude, it’s all about forced induction.
 
WannFly said:
yah, i have been running the numbers based on wind aloft data and temp, but again thats not real time actual temps...

the other route is going south via Rock Springs , which we should probably look at as a backup. i know nothing about mountain flying other than reading a couple of books so being ultra-conservative (read wimpy)
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Rock Springs is a good idea.
 
I had the reverse experience. I learned to fly at BJC. When I moved back east to a sea-level airport, I went to get checked out. After about ten minutes into the flight the instructor asked if I ever intended to throttle back. Now there's an interesting concept, I thought.
 
I took a C-150 up to 13,500 feet once, just to get a picture of the instruments: 10 degrees nose up, airspeed around 35MPH, ROC zero, Throttle full in, mixture all the way out.

I had one of those tanks you slip over the seat back and a full mask.

Once I took the picture, I decided to spin the plane to lose altitude. 33 turns later, I was on a long final for RWY31...
 
WannFly said:
once we saw below 90, we were both taking O2 shots like it was nobody's business
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Problem with the O2 being supplied by cans instead of a bottle connected to a cannula is if something goes wrong in the plane or your bottle gets lost under the seat right when you're already being effected by hypoxia you could become distracted correcting the plane problem. As you've learned, your saturation level drops quickly at those altitudes.
 
I have similar experiences as "flyingron" since my house sits at 6340 MSL and my hangar is at 6880 MSL and I frequently forget to bring the throttle back after taking off from low altitude airports. It is weird to see a manifold pressure greater that 24 inches!! My normal routine is throttle goes full open at takeoff and is only reduced as I descend to land. But that's because my "normal" cruise altitude in my non-turbo Arrow 200 is at least 10 K and more frequently at 12 to 14K over "the rocks". I use a "PulseOx" sensor above 12.5k and if the Vsat drops below 90 I crack open the O2 bottle (cannulas).
 
imwithtuxedo said:
Problem with the O2 being supplied by cans instead of a bottle connected to a cannula is if something goes wrong in the plane or your bottle gets lost under the seat right when you're already being effected by hypoxia you could become distracted correcting the plane problem. As you've learned, your saturation level drops quickly at those altitudes.
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yes, we learnt that first hand.. it was very eye opening moment when you fly over corn fields all day long. i believe i have convinced the PIC to get the those cannula things...
 
Arrow76R said:
I have similar experiences as "flyingron" since my house sits at 6340 MSL and my hangar is at 6880 MSL and I frequently forget to bring the throttle back after taking off from low altitude airports. It is weird to see a manifold pressure greater that 24 inches!! My normal routine is throttle goes full open at takeoff and is only reduced as I descend to land. But that's because my "normal" cruise altitude in my non-turbo Arrow 200 is at least 10 K and more frequently at 12 to 14K over "the rocks". I use a "PulseOx" sensor above 12.5k and if the Vsat drops below 90 I crack open the O2 bottle (cannulas).
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which O2 system are you using?
 
Ryanb said:
HP is torque x RPM (divided by a constant). The rule of thumb is a 3% loss for every 1000ft of altitude gained.

Anything normally aspirated under 300hp is going peak around 12,000ft. After that it will begin to peter out significantly.
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This is something I’ve been wanting to test out myself, my books says I should have 600fpm at 12000 at 2400lbs which is my usual weight. 16.5 service ceiling and 18.5 for absolute in the Cherokee 235 constant speed prop. Wonder how close the books is.
 
Rebel Lord said:
This is something I’ve been wanting to test out myself, my books says I should have 600fpm at 12000 at 2400lbs which is my usual weight. 16.5 service ceiling and 18.5 for absolute in the Cherokee 235 constant speed prop. Wonder how close the books is.
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Please share when you try it out!

One thing that I know effected us from ideal was that the temperature lapse rate between 6500 to 11500 was actually non-existent? So for that part of our climb the DA was increasing faster than we would have expected. I would say if we had an ideal day I could have made it just under 15Kmsl vs the 14Kmsl where we bailed and started back down.

Also I never did anything other than pitch for 85mph the entire time. I think I could have hung on the prop and eeked out even more. But the book recommends best rate of climb (not highest climb possible) at 85mph IAS.
 
imwithtuxedo said:
Problem with the O2 being supplied by cans instead of a bottle connected to a cannula is if something goes wrong in the plane or your bottle gets lost under the seat right when you're already being effected by hypoxia you could become distracted correcting the plane problem. As you've learned, your saturation level drops quickly at those altitudes.
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I still laugh now thinking we could just reach back and grab a can if needed. Once I had it tucked in a easier to reach position it made things much easier.
 
Sinistar said:
I still laugh now thinking we could just reach back and grab a can if needed. Once I had it tucked in a easier to reach position it made things much easier.
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There's always this method.

images
 
Sinistar said:
Yesterday I met up with @WannFly and we did a trial run to get more prepared for a potential trip out to Wyoming this coming fall. It was great having another pilot along for this test as the highest I had been before was 11,000 and this upcoming flight might need higher and thus 02 as well. All data is for a 1972 Cessna 182P (stock 230HP).

We took off from 1450msl at around 75F and DA=2600. The plane was loaded similar to what we will fly. The takeoff roll was nice at about 1000ft with some headwind. There was a very sparse layer of FEW @5500 so no problem going VFR up around/over those.

For this one I flew at 85mph which is recommend for best rate of climb above 10,000. From the ground we were climbing around 1000fpm and held 800fpm to about 7,500. Then the climb rate started dropping to around 550fpm and would continue down to about 0fpm at 14,000. We started with manifold pressure of 23" and was at 9" when we leveled off - didn't expect it to be so low. So we stopped there...but for more than one reason.

Temperatures were a bit weird in that they remained the same from 6,000ft to 11,000ft so it was warmer than the standard lapse rate. The field altimeter was 30.10

This was also the first time I have worked out the engine HP loss based on our altitudes. At 14,000msl we were at DA=15,200ft. The 230HP engine will put out only 125HP at that altitude...wow!!!! In hindsight, its funny to think a fatty Skylane with a fatty pilot can even fly at 125HP.

But we both agreed that most important lesson learned was O2 management.

We had a single oximeter and for this test and probably should have each had our own. It displays heart rate and O2 and once up at the higher altitudes it was easy to mistake one for the other. Later I figured out a different display option I should have used.

We were both showing in the low 90's around DA=10,900. Then after that it started falling off quicker than we had expected. We started seeing numbers in the low 80's (eg 82 & 83) when at DA=12,100ft....DA=15,212ft.

What was more surprising was how quickly those numbers would drop after taking 3 or 4 hits off the 02 cans. I thought a good 3 or 4 hits might last like 10 minutes but I think it was maybe lasting 3-4 minutes. At one point I could start to tell, feeling a bit weak, but he was throwing me a few random math problems and says I didn't screw up any. Now I know what it feels like. I am also a scuba diver. It was not like being narc'd - that is a bit more euphoric. This was a bit more "low energy" which of course makes sense.

In either case we decided since we were using more 02 than we initially guessed that we should head back down and get some fresh air. We spiraled back down which also takes a while. I was in a bit of hurry as I still had one flight left after this. So our ears weren't happy with that descent. On the ground we chatted for about 15 minutes, made sure neither of us were feeling weird and were both still just as stupid and then he drove home and I flew home.

I believe the 182 has a service ceiling of 17,700. Had our day been about 20deg cooler and had the temperature lapse rate been more normal I think we could have reached a DA=17,000 or just a bit less. So fairly close to book numbers.

Thanks for riding with @WannFly! Hopefully your annual wraps up soon so you can get back to flying your baby!
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Great write up. Thanks for taking the time.
 
Real deep slow breaths in and out bring my O2 levels back up at high density altitudes without supplemental oxygen.
 
If buying a new O2 system... the glider folks use fancy ones that really save on O2 loss. Not cheap but a waaaaaay smaller bottle needed, saving space (not an issue in a 182) and weight (not a big deal but nice) and lowering the need to refill very often if you're just hopping ridgelines.

Something to consider. Only going to buy it once, probably.

Our's came with the airplane, standard small bottle and two ports. I have to let the back seat pax pass out if I ever have any hahaha.
 
Remember that Vx and Vy converge as your altitude goes up and service ceiling is a density altitude figure. My Arrow with me and a CFII and full thanks was happy at 12,000 MSL which was 15,000 DA, but any control input made it descend a foot. Pull back, go down. Push forward, go down. Roll or yaw, go down. Change fuel tanks, go down.

Posting mostly for updates about the meet-up.
 
PlasticCigar said:
How does an “oxygen can” satisfy the FAA requirements for supplemental oxygen? Have you considered talking to a CFI before embarking on “Adventures With Hypoxia?” Your write up seems to imply that you are unfamiliar with human physiology and the proper use of aviation oxygen. Might be a good idea to brush up on those before you get hurt.
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I don’t think the FAA defines how supplemental oxygen is to be supplied
 
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iamtheari said:
Remember that Vx and Vy converge as your altitude goes up and service ceiling is a density altitude figure. My Arrow with me and a CFII and full thanks was happy at 12,000 MSL which was 15,000 DA, but any control input made it descend a foot. Pull back, go down. Push forward, go down. Roll or yaw, go down. Change fuel tanks, go down.

Posting mostly for updates about the meet-up.
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I have started another thread on the meet up, under cool places to fly section
 
PlasticCigar said:
No, it says you have to use it DURING THE ENTITE FLIGHT TIME. Not intermittently.:
At cabin pressure altitudes above 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen during the entire flight time at those altitudes;
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Point taken. Just to clarify we spiraled down after hitting 14k, we could never climb any higher and I was running out of math problems to throw at Brad .
 
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