Constant airspeed climb/descent

[FastEddieB]

Not to change the subject or anything, but why is a ten-hour student doing constant speed climbs and descents? Fodder for the basic instrument student, but not for a primary student IMHO. I have no quibble with teaching the pitch-power-trim sequence.

Bob

I think most students from almost the very first day are taught to climb out at a certain speed, either Vy or a selected cruise climb speed. And to control that speed with pitch.

At least that's how my students started out.

If not that way, then how? Just select an approximate pitch and not worry about the speed? I guess that might work, but seems odd.

 

[injb]

Not to change the subject or anything, but why is a ten-hour student doing constant speed climbs and descents? Fodder for the basic instrument student, but not for a primary student IMHO. I have no quibble with teaching the pitch-power-trim sequence.

Bob

6 hours actually

So far the reason I've been doing this is that I have allowed my altitude to change too much without realizing. It seems to happen for various reasons - mostly related to not getting the trim right or too much/too little back pressure during turns. Sometimes I'll push forward or back pressure on the yoke in level flight without even realizing, especially during a distraction, and before I know it I'm a few hundred feet to high or too low.

I understand that the goal is to not let these things happen at all. But until I get to that point, my CFI is on my case about fixing big altitude deviations. I'll be in the middle of a turn and he'll say "by the way you're 200 feet too high, go ahead and fix that too". Sometimes I wish he'd let me practice one thing at a time, but on the other hand I'm sure he knows what he's doing.

 

[arnoha]

6 hours actually

So far the reason I've been doing this is that I have allowed my altitude to change too much without realizing. It seems to happen for various reasons - mostly related to not getting the trim right or too much/too little back pressure during turns. Sometimes I'll push forward or back pressure on the yoke in level flight without even realizing, especially during a distraction, and before I know it I'm a few hundred feet to high or too low.

I understand that the goal is to not let these things happen at all. But until I get to that point, my CFI is on my case about fixing big altitude deviations. I'll be in the middle of a turn and he'll say "by the way you're 200 feet too high, go ahead and fix that too". Sometimes I wish he'd let me practice one thing at a time, but on the other hand I'm sure he knows what he's doing.

The stuff in the first paragraph...that's normal learning stuff. We all do that. Until you've got the turn figured out, figuring out how to correct an altitude excursion isn't going to happen. You're spending too much mental effort on one to actually do the other without screwing up. I think your instructor isn't quite getting that. It's not unusual. For him, he's mastered it. Adding in just the right control input to correct an excursion is child's play. You're not there yet. Sounds like he might be a young instructor.

As for why your initial question was misunderstood: we all jumped on what should be fixed, not what was asked. Good or bad, humans do that. You told us you had a 700' excursion on climb and wanted to fix it. We concentrated on not having that excursion in the first place because 700' is huge. It was a clue that something more basic was not there, and we concentrated on that.

So, for the initial question, how do I fix a 700' oops? Assuming no airspace is about to be busted, I don't touch power, but just pitch down a small amount, a degree or two, and get a 100-200 fpm descent going. I'll pull the power back a touch if it looks like it'll exceed limits in the descent. Trim for comfort. In five minutes, when the desired altitude is there, pitch up to level and return to cruise power if I made a power reduction. Go back to my usual loop on the instruments and outside to ensure the aircraft is doing what I want.

Do it slow. At this stage, every correction like that should be planned to take minutes. If the excursion is 200', a tiny 50 fpm descent will fix it in four minutes. That gives you plenty of time to think about what's happening and not get behind the airplane.

 

[MAKG1]

Climb under full power to cruise altitude. Then do everything at once. Pull the power back, pull the prop back, lean to rpm drop and richen a bit, and trim to level cruise. Continue to trim a bit as speed is gained in level flight. Rudder, elevator and ailerons as needed of course. Trim as needed, all the time.

That works in a 172, but it's not appropriate for all aircraft.

From my own experience, 182s need the throttle backed off to 23 inches (well under full) as soon as safely away from the ground, clean, climbing, and well above obstructions. The exception is a maximum performance climb, and it's not recommended due to engine temperature management. 206s require the PROP to be backed off within 5 minutes. Max takeoff RPM is quite a bit faster than max continuous RPM. In both cases, these actions will occur well before top of climb. During climb, the throttle needs frequent attention as the MP will back off on its own from the altitude, unless it's turbonormalized.

For the 182, if you're actually going somewhere, you push the nose over, close the cowl flaps, trim, and lean (13 GPH). Leave the throttle and prop in climb configuration (23/2400). The 206 can have the throttle and prop pulled back quite a bit and still keep almost all its airspeed, while backing off the otherwise rather thirsty fuel.

 

[MAKG1]

Not to change the subject or anything, but why is a ten-hour student doing constant speed climbs and descents? Fodder for the basic instrument student, but not for a primary student IMHO. I have no quibble with teaching the pitch-power-trim sequence.

Bob

You're right, but I think the student just used the lingo. He's not actually trying to accomplish what an instrument pilot would call a constant airspeed climb. He's just trying to figure out how to level off without screwing up airspeed or altitude.

 

[arnoha]

That works in a 172, but it's not appropriate for all aircraft.

From my own experience, 182s need the throttle backed off to 23 inches (well under full) as soon as safely away from the ground, clean, climbing, and well above obstructions. The exception is a maximum performance climb, and it's not recommended due to engine temperature management. 206s require the PROP to be backed off within 5 minutes. Max takeoff RPM is quite a bit faster than max continuous RPM. In both cases, these actions will occur well before top of climb. During climb, the throttle needs frequent attention as the MP will back off on its own from the altitude, unless it's turbonormalized.

For the 182, if you're actually going somewhere, you push the nose over, close the cowl flaps, trim, and lean (13 GPH). Leave the throttle and prop in climb configuration (23/2400). The 206 can have the throttle and prop pulled back quite a bit and still keep almost all its airspeed, while backing off the otherwise rather thirsty fuel.

All true, but I doubt any of it applies to the training aircraft @injb is using. Actually, what are you using, @injb ? Maybe we can customize our advice.

 

[injb]

All true, but I doubt any of it applies to the training aircraft @injb is using. Actually, what are you using, @injb ? Maybe we can customize our advice.

I'm using a 172 and occasionally a 150.

 

[somorris]

One thing you might want to try, injb, is a light touch on the yoke. I mostly fly with just my thumb and forefinger, barely cradling the yoke. Basically, just enough to be lightly touching it with both the thumb and finger. You don't need a heavy hand. If you need to, increase the pressure just a little during turns, but no need to grab it like you would a shift in the floor. You may be putting elevator pressure on the yoke unconsciously.

 

[exncsurfer]

Having thought about it for a while, I wonder if this is a better way of thinking about it: power is a coarse adjustment for altitude, and pitch is the fine adjustment. You could use pitch as a coarse adjustment, but that would result in big changes to your airspeed as a side affect. Maybe power adjustments are just not precise enough to get the altitude nailed, and that's why you need both? That explains why you would begin a climb or descent with power, but finish it with pitch. It would also mean that having used pitched to fine tune your altitude, you'd be flying at a slightly different airspeed than before, and you have to re-trim. But it would be a small change - a trade off of precise speed for precise altitude control. Does that make sense at all?

I wouldn't think of power at all regarding maintaining level flight(in general). Consider for any power setting (above what can hold you in slow flight), there is one specific pitch that will hold you level. You are using the yoke first, then the trim to find that setting as you get stabilized at a constant speed for a given power.

If you're getting it close then just finding yourself way off later, you're just not scanning instruments often enough. Keep either the vertical speed or the altitude trend in your scan while you're busy doing other things. Make small corrections more often, vs. big corrections. You'll get it after practice, think about when you first tried to steer a car, you may have been bouncing between the lines until you figured out the tiny corrections required to stay straight.

 

[FastEddieB]

If you're getting it close then just finding yourself way off later, you're just not scanning instruments often enough.

I would never downplay good scanning.

But one exercise I did with both primary and instrument students was to find a pitch for level flight, either by looking outside and referencing the real horizon or in the latter case the attitude indicator. At that point I would cover the altimeter and just have them maintain level flight. In relatively calm air after a minute or two I would uncover the altimeter to find it had barely moved. And if the wings were held level, the heading would not have changed either.

It was just an exercise to point out that chasing the altimeter was not necessary if pitch was held constant.

 

[FastEddieB]

One thing you might want to try, injb, is a light touch on the yoke.

A light touch is a worthy goal.

But if a student has climbed 500' above his desired altitude and is headed to 700' above, I'd say a firm hand would be called for more than a light touch.

This may stem from my perceived early failings as a student. I so wanted to be smooth with gentle control inputs that the plane would be all over the place as I tried to coax it tenderly in the direction I wanted it to go. Frustrated my instructor no end. Later with my own students I found similar undercontrolling to be a not uncommon issue.

 

[LongRoadBob]

6 hours actually

So far the reason I've been doing this is that I have allowed my altitude to change too much without realizing. It seems to happen for various reasons - mostly related to not getting the trim right or too much/too little back pressure during turns. Sometimes I'll push forward or back pressure on the yoke in level flight without even realizing, especially during a distraction, and before I know it I'm a few hundred feet to high or too low.

I understand that the goal is to not let these things happen at all. But until I get to that point, my CFI is on my case about fixing big altitude deviations. I'll be in the middle of a turn and he'll say "by the way you're 200 feet too high, go ahead and fix that too". Sometimes I wish he'd let me practice one thing at a time, but on the other hand I'm sure he knows what he's doing.

Just to mention, I'm a low time student too, and I also get a lot of corrections like that as we do level turns, climbs, descend, climbing turns to a new heading, defending turns to new heading or 360 (where I realize about a third of the way through I didn't get a sight picture of the horizon I need to return to) etc.

I too felt like I wish I could just concentrate on hitting the marks, or less things at a time. My CFI will throw a change on me, and as I am getting it throw a new one immidiately before I get the first completed, as I'm doing it. I though a lot about this and realize he is doing this because 1) it's all inter related. I have to be able to get the sight picture and it is coming because of this multi-tasking and expectations and the control is really part of all of the different interactions and 2) I think in flying one cannot take things one at a time, or rather has to get used to feeling overwhelmed and still aiming for as much precision as possible. If you get used to no big deal with being a hundred feet high or low, it is a bad habit.

People mention automobiles, how at one point in time (specially with stick shift) it all seemed so much to handle but with experience it is more natural suddenly but I find with flying...in my experience it is kind of like when I learned cross country skiing here in Norway where it is decidedly not flat. Because both in skiing down a hill and flying the plane is never stopping forward (or downward, but some kind of) motion. Hell, I could barely slow down at all (and then only after learning to balance and take one ski out of the track and use it as a very ineffective brake) and unlike a car where you can stop, you can't just think "ok wait a second here while I figure this out" because you are fifty feet further going fast as you think it.

With my instruction, I had tons of notes, as soon as I got home, that I had compiled while driving home after the lesson like "when he says do a 360, first thing I check is the sight picture" and going over the steps, what I need to do and think about and prioritize at each request.

I am getting a lot of good info to chew on from your post and the replies here. Thanks for that. I think I have been hitting pretty close in leveling off. My CFI stressed that about leveling off, "and wait until you build up speed" (though I got the impression he meant this in leveling off after climb but maybe it is also after a descent) before adjusting power.

Aside from that, I was thinking that the trim you mention, expecting it to work just as well at a different altitude, does this have anything to do with the pressure altitude difference? Or that adding power, even if trimmed will tend to make the nose come up? I'm asking, not suggesting.

One thing, and I don't know if it was intentional on my instructors mind to teach me something, but that blew my mind and made me think harder about basic flight. When we were talking before the last lesson, I knew that the best glide and best climb were different air speeds...and I thought that had something to do with the climb or descent. But he says "why don't we just call it 80 knots".

So that lesson whenever we climbed OR descended I was pitching for 80 knots, and in cruise it was (I believe) the rpm setting while sight picture was level flight that decided.

But I kept going round and round in my mind about this magic number..not specifically 80 but that the same number was used.that 80 knots could be our climb and descend (not optimal, but "good enough" for our purposes that day). Maybe he just tried to make it simpler for me. But it got me to really think about power, and thrust vs. drag.

What I'm getting at, even though I try to be diligent, honestly as a new student reading about the physics of flight and aerodynamics, I (not knowing anything to justify this judgement) somehow decided that the "big thing" was lift on the airfoil, which came with speed...letting drag and thrust take a back seat attention wise.
This 80 knots for descent or climb made me come to grips that I made a mistake there. Unless of course I'm making a new mistake here.

Anyway, I think my CFI can be demanding, and I would prefer to be able to master smaller chunks of flying skills so I could some day out them together, but I totally trust him, know him to be an excellent pilot, and it's enough for me that he has his reasons.

Good luck to you! Anyone that sees me showing a huge mistaken idea, I'm open to correction!

 

[LongRoadBob]

A light touch is a worthy goal.

But if a student has climbed 500' above his desired altitude and is headed to 700' above, I'd say a firm hand would be called for more than a light touch.

This may stem from my perceived early failings as a student. I so wanted to be smooth with gentle control inputs that the plane would be all over the place as I tried to coax it tenderly in the direction I wanted it to go. Frustrated my instructor no end. Later with my own students I found similar undercontrolling to be a not uncommon issue.

But it's all so relative right? I'm wondering, it probably makes more sense to tell a student about using a light touch so they aren't yanking the yoke up, down, left and right, and later let them know they need more authority than the other way around? So far in my limited experience, I am surprised by how little can make such a big change.

It's weird for a new student, takeoffs, maneuvers mostly seem to happen well with a light touch, and then on landings at times it is like "well forget about that, yank that yoke where it needs to be" I'm following my instructors inputs and it seems (with crosswinds) to sometimes be very jerky, and hard...back and forth, but the plane is smooth. I'm seeing that like it can come to be a totally different mindset?

 

[cweinacker]

...fly the plane first...it will come!!!


Sent from my iPhone using Tapatalk

 

[Harold Rutila]

I too felt like I wish I could just concentrate on hitting the marks, or less things at a time. My CFI will throw a change on me, and as I am getting it throw a new one immidiately before I get the first completed, as I'm doing it. I though a lot about this and realize he is doing this because 1) it's all inter related. I have to be able to get the sight picture and it is coming because of this multi-tasking and expectations and the control is really part of all of the different interactions and 2) I think in flying one cannot take things one at a time, or rather has to get used to feeling overwhelmed and still aiming for as much precision as possible. If you get used to no big deal with being a hundred feet high or low, it is a bad habit.
...

One thing, and I don't know if it was intentional on my instructors mind to teach me something, but that blew my mind and made me think harder about basic flight. When we were talking before the last lesson, I knew that the best glide and best climb were different air speeds...and I thought that had something to do with the climb or descent. But he says "why don't we just call it 80 knots".

...

Anyway, I think my CFI can be demanding, and I would prefer to be able to master smaller chunks of flying skills so I could some day out them together, but I totally trust him, know him to be an excellent pilot, and it's enough for me that he has his reasons.

Good luck to you! Anyone that sees me showing a huge mistaken idea, I'm open to correction!

I will suggest that you consider asking your instructor to allow you to make mistakes without him verbalizing corrective action right away. I would tell him exactly what you told us: "I've been feeling a little bit task saturated, and I think if I had some more time to experiment without receiving critique right away, I might be able to get it. Can you give me a task, watch me make the mistake, and then let me try and fix it first?" Sometimes politely-worded feedback like that results us realizing "Wow, I've been talking way too much during these flights."

Regarding Vy and best glide, these two numbers tend to be nearly identical in most piston singles. The lowest point on the total drag curve (which represents the total drag generated by parasitic and induced drag) is the best glide speed. Best glide speed changes with weight. The Vy speed is either identical or very similar, but the Vy speed changes with altitude. For example, in the Grumman Cheetah, the Vy and best glide are both roughly 80 knots at 3,000 feet MSL and at a typical training weight (two pilots and a full tank of gas). For all intents and purposes -- and the intent here is really for you to be able to pitch for a target airspeed -- 80 knots would be appropriate until more precision is demanded as you progress in your skills.

 

[Harold Rutila]

To answer the question about leveling off, and why a simple power addition won't result in the airplane automatically returning to its original cruise pitch when the yoke isn't also adjusted, the answer has to do with the equilibrium of weight, lift, thrust, and drag during a descent. During a constant-speed descent (since that's what we're discussing here), there is equilibrium among all four forces of flight. (Note that this is not the case when the descent is originally entered.) Simply put, power additions destroy that equilibrium.

Most single engine trainers have stability characteristics that result in them always attempting to regain a state of equilibrium. The other controls we have to override that tendency, and in so doing to reset the equilibrium as necessary for the airplane to maintain straight and level flight (as opposed to allowing it to continue descending), are the pitch and the trim.

The design of most single engine training aircraft features a stability characteristic that will result in the aircraft attempting to automatically restore the equilibrium it previously "enjoyed," if you will. In attempting to restore that equilibrium, when the power is added, the aircraft will first pitch up, then down, then continue oscillating until it can regain the equilibrium again. This is called "positive static stability" along the lateral axis.

 

[LongRoadBob]

I will suggest that you consider asking your instructor to allow you to make mistakes without him verbalizing corrective action right away. I would tell him exactly what you told us: "I've been feeling a little bit task saturated, and I think if I had some more time to experiment without receiving critique right away, I might be able to get it. Can you give me a task, watch me make the mistake, and then let me try and fix it first?" Sometimes politely-worded feedback like that results us realizing "Wow, I've been talking way too much during these flights."

Regarding Vy and best glide, these two numbers tend to be nearly identical in most piston singles. The lowest point on the total drag curve (which represents the total drag generated by parasitic and induced drag) is the best glide speed. Best glide speed changes with weight. The Vy speed is either identical or very similar, but the Vy speed changes with altitude. For example, in the Grumman Cheetah, the Vy and best glide are both roughly 80 knots at 3,000 feet MSL and at a typical training weight (two pilots and a full tank of gas). For all intents and purposes -- and the intent here is really for you to be able to pitch for a target airspeed -- 80 knots would be appropriate until more precision is demanded as you progress in your skills.

Our flying club has on the first page of the checklists book, vspeeds listed. Some are slightly different than the POH, for this Piper Warrior II. They have best glide at 73, Vy at 79, and Ven route climb at 87 knots.

As I tried to say, I'm glad he just chose 80, because otherwise I think I would have mistakenly connected the speeds with the action. I mean just the fact that in any plane Vx and Vy are different tells me that would have been wrong to do, but it just drove the point home better using the same exact airspeed for both.

Also I'm glad to see your next post, it was rewarding to see that, though unsure, I was also thinking of the nose wanting to initially raise when one applies power after descent, hoping that trim would get it back to cruise. Here again, in ground school we learn about the types of stability, and your comments (and others here) drove that point home too.

Thanks for the advice, and I had thought along those lines, of mentioning to my instructor, but the thing is I feel like I'm almost there, almost handling the quickly changing instructions as to maneuvers. If it comes up though that I clearly feel I would get more benefit from a do over on something, I'll mention it.

For a new student, I'm seeing that I have to take charge of my learning, that we are working together to help me get the skills needed but at the same time, I realize that I don't see the big picture yet so knowing that my instructor is an excellent pilot, and has instructed for many years, I decided to not try and steer my training and just follow what he is teaching at least until I get more experience.
Last time I felt I didn't do anything right, and I was getting lots of instruction, and I felt worse as time went on, like my head wasn't in the game enough, and as we wound down the lesson, he said "I think your doing good!" Even as I didn't feel that.

Also I threw up on the way back (almost entirely clear water luckily)

Right now I've stopped flying until I get through all of ground school and can take the exam. I need to have taken it to be able to solo. So I will have to relearn again,which I don't mind.

Thanks for the helpful comments!

 

[denverpilot]

Sounds like he might be a young instructor.

He's not, see the videos. (Unless I'm confusing this student with another here, he has videos of the flights.)

From my own experience, 182s need the throttle backed off to 23 inches (well under full) as soon as safely away from the ground, clean, climbing, and well above obstructions. The exception is a maximum performance climb, and it's not recommended due to engine temperature management.

You might be thinking of the 182RG. I believe it has a time limit on takeoff power.

There's no limit from Cessna or Continental requiring 23". Temperature is limiting. If it's hot, you can just climb shallower and faster for more air through the cowl.

(Can't speak for the Lyc-powered newer variety.)

 

[Caramon13]

I used to have some problems getting to and staying at altitude as well. I'd always be 50-75 ft off, usually low instead of high. Which, when I was doing my instrument rating was not a good thing since approaches are +100/-0 in the PTS/ACS for requirements I believe.

My level off routine was never quite "spot on" or was so abrupt people definitely KNEW when I was where I wanted to be..and not in a good way.

I went up with an instructor who gave me a slightly different technique. He told me to be at or near 500 fpm within 1000 ft of the target altitude. Then slowly start backing the climb off, 400 fpm at 400 ft to go, 300 fpm at 300 ft to go..etc..

It was a combination of power and pitch, but if you are climbing at Vy or even a bit above it's definitely pitch to start bring the speed up and shallowing the climb and then bringing the power slowly back as well so that you don't have to overtrim when you reach that altitude.

Was easy to tie the vertical speed to the altitude and my level off's have been pretty smooth since then.

 

[injb]

He's not, see the videos. (Unless I'm confusing this student with another here, he has videos of the flights.)



...

No you must be thinking of someone else. I have some videos but haven't posted any on the internet. I think my instructor is around 40 or so.

 

[gismo]

I used to have some problems getting to and staying at altitude as well. I'd always be 50-75 ft off, usually low instead of high. Which, when I was doing my instrument rating was not a good thing since approaches are +100/-0 in the PTS/ACS for requirements I believe.

My level off routine was never quite "spot on" or was so abrupt people definitely KNEW when I was where I wanted to be..and not in a good way.

I went up with an instructor who gave me a slightly different technique. He told me to be at or near 500 fpm within 1000 ft of the target altitude. Then slowly start backing the climb off, 400 fpm at 400 ft to go, 300 fpm at 300 ft to go..etc..

It was a combination of power and pitch, but if you are climbing at Vy or even a bit above it's definitely pitch to start bring the speed up and shallowing the climb and then bringing the power slowly back as well so that you don't have to overtrim when you reach that altitude.

Was easy to tie the vertical speed to the altitude and my level off's have been pretty smooth since then.

That is the right technique (make the vertical speed proportional to the altitude difference) for flying on the instruments but maybe a bit too complex for a new primary student.

 

[gismo]

Right now I've stopped flying until I get through all of ground school and can take the exam. I need to have taken it to be able to solo. So I will have to relearn again,which I don't mind.

Thanks for the helpful comments!

Unless things have changed you don't need to have passed the PPL written test before you solo. You do have to pass a pre-solo quiz but your CFI gives you that AFaIK.

 

[Caramon13]

That is the right technique (make the vertical speed proportional to the altitude difference) for flying on the instruments but maybe a bit too complex for a new primary student.

Yeah, for a VFR private pilot, eyes should be out the window I know, but coming up on altitude you're probably looking at the instruments a bit, helps to crosscheck and work on technique.

Tools for consideration . It does work well when you are under the hood though, so maybe when he does some simulated time it'll help?

 

[gismo]

He's not, see the videos. (Unless I'm confusing this student with another here, he has videos of the flights.)



You might be thinking of the 182RG. I believe it has a time limit on takeoff power.

There's no limit from Cessna or Continental requiring 23". Temperature is limiting. If it's hot, you can just climb shallower and faster for more air through the cowl.

(Can't speak for the Lyc-powered newer variety.)

And a small reduction in MAP from full throttle will actually raise the EGT and CHT on most engines. Unless this is required in the POH Limitations section or by TCDS required placard I wouldn't do that.

 

[gismo]

The lowest point on the total drag curve (which represents the total drag generated by parasitic and induced drag) is the best glide speed. Best glide speed changes with weight. The Vy speed is either identical or very similar, but the Vy speed changes with altitude.

FWIW, max L/D (best glide speed) isn't at the bottom of the drag curve, in zero wind it's the tangent to that curve on a line from the graph's origin.

 

[exncsurfer]

Unless things have changed you don't need to have passed the PPL written test before you solo. You do have to pass a pre-solo quiz but your CFI gives you that AFaIK.

Yea, he is in Europe somewhere, he mention that is a requirement where he is.

 

[MAKG1]

And a small reduction in MAP from full throttle will actually raise the EGT and CHT on most engines. Unless this is required in the POH Limitations section or by TCDS required placard I wouldn't do that.

Reducing 29 inches to 23 is not small.

While it's not a "limitation" (it's explicitly allowed for a maximum performance climb), your CHT does have limitations, both practical and legal. If you don't want really hot CHT's, you don't climb at full throttle from sea level to 5000 (an effective local minimum for IFR flight). I can't go much above 23 inches at Vy if I want to keep my CHTs below 400 F, which is what our mechanic recommends.

 

[dmspilot]

FWIW, max L/D (best glide speed) isn't at the bottom of the drag curve

Yes it is.
L/D max stands for maximum lift/drag. Since lift is constant (equal to the weight of the airplane) it is self evident that this occurs at the lowest point in the drag curve.

 

[gismo]

Reducing 29 inches to 23 is not small.

While it's not a "limitation" (it's explicitly allowed for a maximum performance climb), your CHT does have limitations, both practical and legal. If you don't want really hot CHT's, you don't climb at full throttle from sea level to 5000 (an effective local minimum for IFR flight). I can't go much above 23 inches at Vy if I want to keep my CHTs below 400 F, which is what our mechanic recommends.

I agree completely with the 400°F limit but all you need to do is lower the nose and climb at a higher speed. And if you can't keep the cylinders cool with a full rich mixture you might have some baffle problems and/or too low a FF. That said, you're not gonna hurt anything if you keep the CHTs under control and climb with 23 inHg MAP but I'd be surprised if you couldn't get the same FPM of climb at max continuous power while keeping the cylinders cool with the resulting airspeed increase.

 

[gismo]

Yea, he is in Europe somewhere, he mention that is a requirement where he is.

Ahh, that does make a big difference.

 

[LongRoadBob]

Ahh, that does make a big difference.

Yes, in Norway. Most of the rules are very close, but I'm seeing some differences in some areas.

 

[gismo]

Yes it is.
L/D max stands for maximum lift/drag. Since lift is constant (equal to the weight of the airplane) it is self evident that this occurs at the lowest point in the drag curve.

You're right, my bad. I had a power required curve stuck in my head.