XC Altitude selection

[Jaybird180]

I'm planning a trip via rental Skylane from DC to Atlanta (KPDK) and wanted some thoughts about using 10,500 as the chosen enroute altitude.

I chose that altitude as 2,000 above the highest obstacle according to sectional blocks and then adding VRF cruising rules. I should be able to return at 9,500.

Also, since this will be my first flight above 10k, I thought it might be a good idea to purchase an oximeter and some O2. I would appreciate suggestions there also, as I don't expect to need the O2 during or after the flight, but its just in case.

 

[gismo]

I'm planning a trip via rental Skylane from DC to Atlanta (KPDK) and wanted some thoughts about using 10,500 as the chosen enroute altitude.

I chose that altitude as 2,000 above the highest obstacle according to sectional blocks and then adding VRF cruising rules. I should be able to return at 9,500.

Also, since this will be my first flight above 10k, I thought it might be a good idea to purchase an oximeter and some O2. I would appreciate suggestions there also, as I don't expect to need the O2 during or after the flight, but its just in case.

I doubt that you'd need oxygen for that altitude but I've noticed that if I spend a lot of time above 9000 MSL I'm noticeably less fatigued and suffer fewer headaches if I use enough O2 to keep my spO2 at 90% or higher. I've seen pulseOx units for less than $30 so I think at the very least you should buy and use one if there's any chance you're going higher than 8000. If you want to take O2 along you may be able to borrow or rent a portable system.

BTW I checked the altitudes along the route from DC to KPDK and it looks like there's nothing over 3-4000 if you remain east of the mountains and with a route right above the mountains I didn't find much above 6000 with any plausible route. If there's much wind, it's a good idea to stay at least a couple thousand above the ridges but I don't think you'd need to fly as high as you suggested. Typically when VFR your altitude will be dictated by terrain, clouds, tubulence, and wind in that order and it's likely that all of those will change before and even during the flight. Finally, you should consider using different altitudes along the way, especially when VFR and or near mountains rather than picking a single height for the entire trip. On long trips I usually check the conditions which could affect my optimal altitude every 100-200 miles and adjust accordingly.

 

[SkyHog]

I'm planning a trip via rental Skylane from DC to Atlanta (KPDK) and wanted some thoughts about using 10,500 as the chosen enroute altitude.

I chose that altitude as 2,000 above the highest obstacle according to sectional blocks and then adding VRF cruising rules. I should be able to return at 9,500.

Also, since this will be my first flight above 10k, I thought it might be a good idea to purchase an oximeter and some O2. I would appreciate suggestions there also, as I don't expect to need the O2 during or after the flight, but its just in case.

Having flown at high altitudes, I can say that 12,000 is where you will start to be affected. But on the east coast, why go so high, unless for wind benefits? 4,500 and 5,500 should be fine for that fight. Note that you'll be flying right over my home doing it.

 

[Clark1961]

While O2 and and oximeter are all well and good, is there any real terrain & obstacle reason to climb above 6,500'? It looks like the highest terrain along that route is 3,500'.

It might be nice to go to 10 for cooler air and to be above the riff-raff , but going to 10 in a 172 is a slow process. If you do climb that high, don't forget to lean. Also don't forget to richen on descent or it'll get really quiet.

 

[Jaybird180]

Maybe I misread the terrain on the sectional? i know I have to cross the Blue Ridge Mountains.

 

[azure]

Maybe I misread the terrain on the sectional? i know I have to cross the Blue Ridge Mountains.

Maybe. I don't think there are any summits in that range much over 5,000 MSL. The highest of the Appalachians is in NC and doesn't even reach 7,000. Over 10,000 is probably overkill. I've never flown over them, but don't see any reason to go higher than 8,500 westbound or (at most) 9,500 eastbound -- more likely 7,500.

 

[Ghery]

Those are my altitudes crossing the Cascade mountains in Washington state. I didn't know there was anything in GA that would make you want to go that high.

 

[TMetzinger]

8500 should be fine, in fact 6500 might be good enough.

Everyone is different as far as O2 goes - you should be fine without it at 10,000, but you may still see some benefits from Oxygen. I normally put on O2 at 6000 at night, and at 10,000 during the day.

 

[Jaybird180]

I looked at my course again. If I fly the pink line, 6500WB and 7500EB keeps me out of trouble. If I deviate off course to the north, another 2000ft keeps me safe. I must have been looking too many sectors off my course when I came up with 10,500

 

[Jaybird180]

Unless I'm flying early in the morning, I try to avoid altitudes within the boundary layer, especially between 4,000 and 6,500 feet. This is typically near the top of the haze layer making it difficult to see while you are being bumped around in thermal turbulence. I try to get above this whenever possible especially on longer flights...

What cruising altitudes would you recommend, considering that most likely we'd takeoff in the wee-morning hours.

 

[EdFred]

Heading west you generally want to fly as low as you can. (Headwinds)

 

[Let'sgoflying!]

tailwinds - climb high, then pull it way back and float along.
headwinds - 'hedgehop' and firewall it.

modified by weather, terrain, airspace, traffic congestion, engine limits, passenger comfort, etc etc

 

[mcarlini]

going to 10 in a 172 is a slow process.

Try a 150 in the middle of summer

 

[rpadula]

I, too, am having a hard time figuring out where you'll need to go as high as 10.5k. What route are you planning, Jay?

 

[Jaybird180]

I've reworked the route a couple times since posting. I'll pull it off my iPad and post (if I saved it as a fav). Altitude is MUCH lower now. Sorry I didn't make that clearer.

 

[rpadula]

I've reworked the route a couple times since posting. I'll pull it off my iPad and post (if I saved it as a fav). Altitude is MUCH lower now. Sorry I didn't make that clearer.

Roger that. Of course, in the summer, altitude in a GA aircraft is Nature's air conditioning.

 

[Jaybird180]

That's nice, but yesterday I looked at winds aloft and it can get up to 37kts HEADWIND. I'm not flying the SST.

 

[Skylane81E]

That's nice, but yesterday I looked at winds aloft and it can get up to 37kts HEADWIND. I'm not flying the SST.

Wind is your master, pull out your E6B and your performance tables and see what the wind and "trueing out" do to you.

I've been known to ride tailwinds at 13,500 east bound and slog it out 1000AGL when west bound.

On the rare days when wind isn't a factor (or when I have a tail wind) I sometimes climb to my target manifold pressure then pull the prop back and lean, leaving the throttle wide open.

 

[denverpilot]

Roger that. Of course, in the summer, altitude in a GA aircraft is Nature's air conditioning.

Didn't work over the desert southwest in the 182 in July a few years ago.

 

[denverpilot]

8500 should be fine, in fact 6500 might be good enough.

Everyone is different as far as O2 goes - you should be fine without it at 10,000, but you may still see some benefits from Oxygen. I normally put on O2 at 6000 at night, and at 10,000 during the day.

Heh. You'd need O2 at 20' AGL here at night. Pattern altitude is 6885'. Normal cruise for me, stored in my FF and other online flight planning profiles is 9500'.

I'm trying to imagine the weird looks I'd get if I whipped out the O2 for night pattern work.

I know, I know. I have more red blood cells than flatlanders. It makes drinking at sea level that much more fun too. Can usually drink anyone not from here under the table without trying very hard. Ha. Oops I let the Denverites' secret out of the bag!

The first couple of beachfront cocktails in Hawaii were like, "Was there even any alcohol in that?"

 

[Jaybird180]

What route are you planning, Jay?

Think 6500 will work west-bound and 7,500 east for this:

Route 1: vkx>mtv>pdk
Route 2: vkx>pvg>5w8>pdk

Landing at each. Obviously, the vkx>pvg leg doesn't need the altitude and winds are usually coming from 220-250 so that's a headwind.

 

[Henning]

Heh. You'd need O2 at 20' AGL here at night. Pattern altitude is 6885'. Normal cruise for me, stored in my FF and other online flight planning profiles is 9500'.

I'm trying to imagine the weird looks I'd get if I whipped out the O2 for night pattern work.

I know, I know. I have more red blood cells than flatlanders. It makes drinking at sea level that much more fun too. Can usually drink anyone not from here under the table without trying very hard. Ha. Oops I let the Denverites' secret out of the bag!

The first couple of beachfront cocktails in Hawaii were like, "Was there even any alcohol in that?"

Never worry about weird looks. You might want to perform a little experiment with O2 in the pattern at night and see if you see a difference. If you do, you might consider taking a few hits of O2 when you're coming into the pattern. Just because you live at altitude and you body is used to the effects of running on low O2, that does not equate with not being benefited by extra O2. Hypoxia is an incipient thing, and it is not "on/off" either. You can get slightly dulled over a matter of time and not realize the issue. 99.95% of the time for a rated pilot, being mildly hypoxic will have no negative repurcussions, but the other .05% of the time when the feces have escaped into the airmover, every little thing counts. I had an interesting experience with Bob Gerace when we were in his T-310-R. We were both hypoxic as we were conserving O2 for after dark (I think we were around 15,000') when we had an engine fail. We handled it well, no control issues or anything, but it was over a minute before one of us remembered to swap the fuel valve (we had had issues with that engine's turbo wastegate controller and just assumed the engine had s- itself). Both of us know full well that the fuel valve is the first thing you reach for. Heck, he had come back from his recurrent at Flight Safety recently. Neither of us felt bad, we were having a normal conversation when it happened, but neither of us reached for the fuel valve or the checklist when it went down, and that's all it was, we ran an aux dry. Something I've done hundreds of times at much lower altitudes and just reached down and swapped tanks.

It's the little things that mess you up, and it's the little hedges that add up to keep you safe.

 

[COFlyBoy]

Never worry about weird looks. You might want to perform a little experiment with O2 in the pattern at night and see if you see a difference. If you do, you might consider taking a few hits of O2 when you're coming into the pattern. Just because you live at altitude and you body is used to the effects of running on low O2, that does not equate with not being benefited by extra O2.

I think the point was that those of us who live at 5280 have blood that is fully oxygen saturated on the ground (or nearly so). Going up to 6000' doesn't cause us to suddenly become hypoxic. The whole use O2 above 5k at night probably is based on a typical American. The typical American lives a lot closer to sea-level.
I think a good rule would be if you are 5000 feet above your aclimated/normal elevation, then you should use oxygen at night.

 

[Henning]

I think the point was that those of us who live at 5280 have blood that is fully oxygen saturated on the ground (or nearly so). Going up to 6000' doesn't cause us to suddenly become hypoxic. The whole use O2 above 5k at night probably is based on a typical American. The typical American lives a lot closer to sea-level.
I think a good rule would be if you are 5000 feet above your aclimated/normal elevation, then you should use oxygen at night.

Have you ever tried it to see if there was an advantage for you personally? It costs you next to nothing to try. Always good to know where you might be able to find an edge.

 

[Jeanie]

Jay, remember that you can change your altitudes as you fly along also so if it's not working for you then just climb/descend as needed. And if you do climb to a fairly high AGL altitude - and we know that takes time in a 172 (I fly a 152 so well, it really takes time) you might consider starting a 50-100 ft/min. cruise descent as you get near your destination to which will speed you up somewhat and maybe make up for some of the time on the front end of the trip.
I started a slow descent some 38 miles out from my destination lately and gained 15 kts and by the time I got there I was right at pattern altitude....
Have a good trip.

 

[COFlyBoy]

Have you ever tried it to see if there was an advantage for you personally? It costs you next to nothing to try. Always good to know where you might be able to find an edge.

I'll see if I can bum an O2 bottle from someone. I've flow a fair amount above 10k (like almost all of my cross country flying) and not noticed any hypoxic symptoms. I think the difference may be hard to notice.

 

[gprellwitz]

I'll see if I can bum an O2 bottle from someone. I've flow a fair amount above 10k (like almost all of my cross country flying) and not noticed any hypoxic symptoms. I think the difference may be hard to notice.

I think it's likely that the difference may be hard to notice while you're hypoxic! If, OTOH, you go on O2, my guess is that it'll become a little more obvious. I remember one time Leslie and I were up around 11,000 and we were definitely noticing that some simple math problems were taking a little longer than they should and that we were getting a little snippy. We requested lower, and the symptoms went away.

 

[Jeanie]

I flew at 11,500 this past weekend back from Dona Ana (just west of El Paso) to Alpine for a couple hours and was very cognizant of possible hypoxia, the density altitude was 14,000... so I kept checking myself but then thought it was pretty funny because how would I know if I wasn't sufficiently OK? I didn't feel odd, or get a headache etc but like ya'll have said... the effects are insidious.
I think I'm going to try to borrow someone bottle and use it sometime to see if I notice a difference.

 

[Henning]

I'll see if I can bum an O2 bottle from someone. I've flow a fair amount above 10k (like almost all of my cross country flying) and not noticed any hypoxic symptoms. I think the difference may be hard to notice.

Hypoxia symptoms are self masking. The difference of minor hypoxia that takes say 15 IQ points is almost impossible to notice until you go on O2, and then it's nearly instantaneous to notice if there is a difference.

 

[Jaybird180]

Jay, remember that you can change your altitudes as you fly along also so if it's not working for you then just climb/descend as needed. And if you do climb to a fairly high AGL altitude - and we know that takes time in a 172 (I fly a 152 so well, it really takes time) you might consider starting a 50-100 ft/min. cruise descent as you get near your destination to which will speed you up somewhat and maybe make up for some of the time on the front end of the trip.
I started a slow descent some 38 miles out from my destination lately and gained 15 kts and by the time I got there I was right at pattern altitude....
Have a good trip.

Thanks, I'll keep this in mind as I fly the DA-40

 

[Jeanie]

Thanks, I'll keep this in mind as I fly the DA-40

OK OK, making up speed isn't needed in your very nifty DA40... nevermind.. for some reason I thought you were going in a 172... must've not read something right or gotten some posts confused.


Have a good flight going "fast"

 

[denverpilot]

Never worry about weird looks. You might want to perform a little experiment with O2 in the pattern at night and see if you see a difference.

Yeah, I need to go get night current this weekend if possible, anyway -- so I'll throw the bottle in. I hear the effect on the rods/cones in the ol' Mark I Eyeball is quite pronounced... the world can sometimes get a bit brighter as you turn on the flow...

O2 system needs a checkout anyway, and I need some night time -- so will see if it seems to make any difference...

 

[Jaybird180]

OK OK, making up speed isn't needed in your very nifty DA40... nevermind.. for some reason I thought you were going in a 172... must've not read something right or gotten some posts confused.


Have a good flight going "fast"

I said Skyhawk in the original post

Then when I told my wife how long it would take to get there...

 

[Jeanie]

I said Skyhawk in the original post

Then when I told my wife how long it would take to get there...

~~~~ Ah, I see, and she isn't interested in you building cross country time. Some day I'd like to fly a DA 40 just to see what they are like.

I bet ya'll will have a good time

 

[Henning]

~~~~ Ah, I see, and she isn't interested in you building cross country time. Some day I'd like to fly a DA 40 just to see what they are like.

I bet ya'll will have a good time

In the summer in Alpine TX, it will be hot and I suggest you wear a helmet and strap in tight because they ride rougher than most in rough air.

 

[rpadula]

Think 6500 will work west-bound and 7,500 east for this:

Route 1: vkx>mtv>pdk
Route 2: vkx>pvg>5w8>pdk

Landing at each. Obviously, the vkx>pvg leg doesn't need the altitude and winds are usually coming from 220-250 so that's a headwind.

I ran route 1 through the AOPA flight planner and it looks like you'll be fine at 6500.

One comment about route 2: the direct route from 5W8 to PDK goes straight through the CLT airspace. 99% of the time, they will make you go around the Class B there.

 

[Jaybird180]

Some day I'd like to fly a DA 40 just to see what they are like.

Do it, do it, do it
With your aerobatic background, you'll love the power-on stalls (gotta work the rudder or she'll drop whatever wing and will start an incipient spin if you let it). With that said, there is so much warning that even an Airbus pilot won't get it wrong.


Rich- I haven't played much with the AOPA planner. What's that inset box, bottom right?

In the summer in Alpine TX, it will be hot and I suggest you wear a helmet and strap in tight because they ride rougher than most in rough air.

Can't- Inertial reel shoulder harness (automotive style).

I'm 6'1" and I don't have any concerns about hitting my head on the canopy.

 

[rpadula]

Rich- I haven't played much with the AOPA planner. What's that inset box, bottom right?

Me neither, but that's just a profile view window. Look up near the top under the "Weather" and "Pilot" tabs, and you'll see "Profile View" in smaller text. That brings up terrain vs. your altitude for the route.

 

[Sac Arrow]

Oh jeez, we call mountains that peak at 5,000 feet "hills" here. That's still flatlands to us. Your actual enroute altitude should ideally be based on the winds aloft prediction for your route - at least that's what I do on a long flight. Usually if I'm flying over flat ground (the Valley) for more than an hour I'll usually cruise somewhere between 6,500 and 7,500 if winds don't favor other altitudes. If I'm going to, say San Diego, I'll cruise between 10,500 and 11,500 just to fly over Bravo airspace.

I personally find that right around 11,000 is where I find oxygen to be beneficial.

 

[Jaybird180]

Oh jeez, we call mountains that peak at 5,000 feet "hills" here. That's still flatlands to us. Your actual enroute altitude should ideally be based on the winds aloft prediction for your route - at least that's what I do on a long flight. Usually if I'm flying over flat ground (the Valley) for more than an hour I'll usually cruise somewhere between 6,500 and 7,500 if winds don't favor other altitudes. If I'm going to, say San Diego, I'll cruise between 10,500 and 11,500 just to fly over Bravo airspace.

I personally find that right around 11,000 is where I find oxygen to be beneficial.

Based on how you feel or an oximeter?