Reasons the takeoff climb would use a different vspeed than Vy

[LongRoadBob]

I have searched and was sure I responded in the last month with thanks for someone that asked about this. That the takeoff speed climb out was different than the Vy.

I thought I remembered replying to the effect of "thanks! I was going to ask my instructor about this but now don't have to" and yup...I forget the answer.

I did due diligence and tried to find all threads I have replied to but can't find it.
In my case the checklist has climb out from takeoff at 76 knots, but Vy is 79 knots. (IAS). Further, listed is V en route climb is 87 KIAS and I'm still not sure what that is or why it is so much higher.

I recall the OP of that thread getting an answer that seemed to make sense but cannot recall what it was. Anyone remember or know why it would be this way?

 

[RyanB]

Enroute climb offers better efficiency and cooling of the engine.

 

[ircphoenix]

I'll use my airport as an example.

We have some pretty stringent noise abatement procedures. So often times we use Vx, especially on a touch and go, to get as much altitude over the shortest lateral distance so by the time we cross the fence, we're high enough that we don't anger the noise sensors.

Vy is the fastest climb... which you might need for something like getting enough altitude in a hurry before entering the route through the LAX bravo.

Anywhere between those two numbers and you're gaining more of one and sacrificing more of the other.

Enroute climb is for when you're not in any hurry to climb, so you don't need Vy or Vx, and can settle for a gradual climb with max airflow over the engine to keep the engine cool.

 

[Trailboss]

I will usually climb above Vy. Better forward visibility, more airflow over the engine, and better ground speed. Once I'm above TPA and out of the airport area, I'd rather get across the ground rather than above it.

 

[MAKG1]

In general, Vx is for obstacle avoidance, but it trades off engine cooling, so you don't want to do it very long. VFR, to clear airspace, there is no reason not to circle for altitude instead, at Vy. It will take less time and cost you a bit less, plus it's better for visibility and the engine.

Vy is the low-altitude default. Use it if there is no reason to use anything else.

Faster than Vy is used where altitude isn't so critical, but forward visibility and cooling are desired. Typically, I'll use that above TPA. 90 knots or 500 FPM, whichever is slower, no slower than Vy adjusted for altitude.

Note that Vy falls with altitude, so if it's hot as hell and you're not at sea level, you may need a bit more pitch to get the best climb. It's always greater than Vx (at any altitude).

There used to be a noise abatement advisory to climb to TPA at Vx, at Truckee. Mercifully, that's gone, as it's a really stupid thing to do at a mountain airport. As always, safety trumps noise abatement.

 

[SoCal RV Flyer]

My Vy is about 82 KIAS, but 90-95 is the sweet spot for me, for all the above mentioned reasons. The RVs are pretty tightly cowled for lower drag, so cooling on climb-out can be a consideration...especially on these 100-degree days.

 

[denverpilot]

Climbing slower than Vy is usually so you can use Vx.

Climbing faster than Vy is usually so you'll be lower and further away from the airport when the engine quits.

 

[jordane93]

Better visibility in front of the nose.

 

[SoCal RV Flyer]

Depending on where the engine quits (and what surrounds you particular airport), a landing on a golf course, road, open field, etc. might be preferable to the "impossible turn" and ensuing stall/spin that has killed hundreds of pilots. I'm far more worried about hitting another plane in the pattern because I'm climbing out at 1700 fpm (and can't see squat over the nose) than I ever will be about the engine quitting.

 

[denverpilot]

Depending on where the engine quits (and what surrounds you particular airport), a landing on a golf course, road, open field, etc. might be preferable to the "impossible turn" and ensuing stall/spin that has killed hundreds of pilots. I'm far more worried about hitting another plane in the pattern because I'm climbing out at 1700 fpm (and can't see squat over the nose) than I ever will be about the engine quitting.

You often see head on traffic at the end of the runway you're departing on in that 36 seconds it took you to climb above pattern altitude and that was low enough they had to climb into you from below to remain invisible below your cowl? Especially one you didn't know was there when you shoved the throttle up?

 

[Hank S]

Depending on where the engine quits (and what surrounds you particular airport), a landing on a golf course, road, open field, etc. might be preferable to the "impossible turn" and ensuing stall/spin that has killed hundreds of pilots. I'm far more worried about hitting another plane in the pattern because I'm climbing out at 1700 fpm (and can't see squat over the nose) than I ever will be about the engine quitting.

If it bothers you that much, lower the nose some so you can see oncoming traffic!

 

[midlifeflyer]

I have searched and was sure I responded in the last month with thanks for someone that asked about this. That the takeoff speed climb out was different than the Vy.

I thought I remembered replying to the effect of "thanks! I was going to ask my instructor about this but now don't have to" and yup...I forget the answer.

I did due diligence and tried to find all threads I have replied to but can't find it.
In my case the checklist has climb out from takeoff at 76 knots, but Vy is 79 knots. (IAS). Further, listed is V en route climb is 87 KIAS and I'm still not sure what that is or why it is so much higher.

I recall the OP of that thread getting an answer that seemed to make sense but cannot recall what it was. Anyone remember or know why it would be this way?

"The checklist"? Whose? The manufacturer's? Your personal one? The flight school's?

If yours or the flight school's and it is different from the manufacturer's, I don't know.

If the manufacturer's, is takeoff to be done with flaps? If so, initial climb will be typically done at a speed lower than clean Vy, transitioning to clean Vy as you retract the flaps. Could also be a transition to raising gear in a retract. The aircraft manual might also have an expanded section in the Normal Operations section that explains the difference.

V-enroute is just a speed that you transition to once at an initial target altitude, typically at or near pattern altitude. The presumption is that you no longer need to get high as quickly as possible and can lower the nose, see traffic in front of you more easily, travel forward faster, and have better engine cooling on a warm day, all at the same time,

 

[flyingron]

Visibility and engine cooling. Both Vx and Vy in my plane are incredibly nose up attitudes. Once I have some altitude and am clear of obstacles, I lower the nose.

 

[Capt. Geoffrey Thorpe]

The best way is to zoom climb if you have a RV something-or-a-number.

 

[LongRoadBob]

"The checklist"? Whose? The manufacturer's? Your personal one? The flight school's?

If yours or the flight school's and it is different from the manufacturer's, I don't know.

If the manufacturer's, is takeoff to be done with flaps? If so, initial climb will be typically done at a speed lower than clean Vy, transitioning to clean Vy as you retract the flaps. Could also be a transition to raising gear in a retract. The aircraft manual might also have an expanded section in the Normal Operations section that explains the difference.

V-enroute is just a speed that you transition to once at an initial target altitude, typically at or near pattern altitude. The presumption is that you no longer need to get high as quickly as possible and can lower the nose, see traffic in front of you more easily, travel forward faster, and have better engine cooling on a warm day, all at the same time,

First off...as always, thanks guys for a lot of good information!

To your specific post, it is the flight school checklist. It's a little unclear why it is that way. I mean maybe I missing something but we are at full throttle no matter what, but it might still be a noise thing? We have s higher pattern than normal (1500 ft.) and I'm just not sure.

I'm aware of (at least theoretically) Vx but in the same checklist Vx is 63 KIAS.
When I asked about the checklist for take off climb out being 3 KIAS lower than Vy, he seemed to think it might be a mistake, and that maybe we should use 79 from now on.

Thanks also all for V en route, that makes total sense to me.

I still wish I could find that thread (from a month or so ago), I thought I answered something like "this is great, I wondered too and now don't have to ask my instructor" but maybe I worded it differently or never sent because it was just a dumb message of not much worth. I tried searching all posts I've commented in but either missed it or I never answered. I seem to recall an "A Ha..." Experience with the answers. Maybe it was noise, or cooling, I just don't know. If anyone remembers it (or the OP of it reads this) please let me know. Again, thanks all!

 

[Wrench978]

Here you go.

https://www.pilotsofamerica.com/community/threads/enroute-climb.96958/#post-2107328

 

[PPC1052]

Further, listed is V en route climb is 87 KIAS and I'm still not sure what that is or why it is so much higher.

Since this is the school's checklist, not the manufacturer, their en-route V climb rate may be their best estimate of what will give you a 500 foot per minute climb rate in a clean configuration. Of course, that rate varies with altitude and ambient conditions. Knowing what speed gives a 500 foot per minute climb rate is not that important for VFR, but it may be useful for IFR where you are expect to maintain at least that climb rate so that ATC can project whether there will be conflicts with assigned routes and altitudes.

 

[SoCal RV Flyer]

You often see head on traffic at the end of the runway you're departing on in that 36 seconds it took you to climb above pattern altitude and that was low enough they had to climb into you from below to remain invisible below your cowl? Especially one you didn't know was there when you shoved the throttle up?

I fly out of a nontowered airport, with planes approaching from the north and south. A few of them NORDO; and a few of them no doubt making fewer radio calls than they should. These are all good reasons to be able to see over the nose. The plane departing in front of me? No problem whatsoever.

 

[SoCal RV Flyer]

If it bothers you that much, lower the nose some so you can see oncoming traffic!

Precisely what I'm doing by climbing out at 90 KIAS! At which speed I'm probably outclimbing your typical 172.

 

[denverpilot]

I fly out of a nontowered airport, with planes approaching from the north and south. A few of them NORDO; and a few of them no doubt making fewer radio calls than they should. These are all good reasons to be able to see over the nose. The plane departing in front of me? No problem whatsoever.

You didn't answer the question.

 

[denverpilot]

I fly out of a nontowered airport, with planes approaching from the north and south. A few of them NORDO; and a few of them no doubt making fewer radio calls than they should. These are all good reasons to be able to see over the nose. The plane departing in front of me? No problem whatsoever.

You didn't answer the question.

And the reason I'm asking is simple... Do you just *want* to see, or can you mathematically justify the lowered climb profile?

Here's the common sense version:

In 20 years of flying I've seen orders of magnitude more accidents from loss of takeoff power than from midair collisions during departure, controlled or uncontrolled airport, doesn't matter.

When you depart at Vy there's some small angle of elevation between the ground and your sight line that you can't see. (If you make slight s-turns much of that reappears, but we'll leave out that technique.)

What's the angle blocked in your aircraft, and how often have you actually seen aircraft there inside that angle climbing up into you at the departure end of a runway that you couldn't see before starting the takeoff roll?

Takeoffs are a calculated and planned statistics game. Which statistics are you basing your plan on? Or is it all just emotion?

I even did the math for you, since you provided a climb rate. Your window of collision danger drops dramatically above pattern altitude, so you're trading 36 seconds of maximum performance climb through TPA, which might be used to save your butt, for what? 10 more seconds of better visibility toward an area unlikely to have oncoming traffic?

That's all I'm asking you to consider. You're the PIC. It's your plan. You can even extend the math and see how much further out your climb profile takes you and where the graph lines cross for a safe return to the departure runway. 36 seconds to TPA from positive rate, is pretty good numbers.

I can't hit that. Airliners can, and they even have a guarantee of a climb rate if they trash an engine, and they still start their standard departure profile with a steep angle.

In a single, you're more likely to want to extend that high angle longer than they, if you're flying it by the statistics of what will really bite you in the ass the hardest during takeoff.

You do however, have excess airspeed, and only you can decide if you're good enough to use it to your advantage in a high performance turn if the mill quits, and know how wide of a radius that turn would be compared to starting it at Vy and lowering the nose instead.

 

[flyingron]

I've seen more airplane engines killed due to excessive heat production than midairs, if you want to talk anecdotes.

 

[SoCal RV Flyer]

As I stated before, there are other considerations to the faster, shallower climb too, engine cooling being near the top of the list during our recent 105 F days. I prefer the better visibility in my own nontowered Wild West corner of airspace. Our standard pattern entry is left crosswind over the numbers (we're in a little fishmouth cutout of Ontario's Class C) so a very steep climb may blank out that NORDO Aeronca on crosswind. As for engine failure, at 90 KIAS I've got a boatload of extra kinetic energy (as you point out), and less of a forward push to establish best glide than I'd have at Vx or Vy...so maybe a little altitude saved in the transition. I've scouted my airport for possible engine-out landing sites, so if the engine decided to quit at the dreaded 350'-400' AGL, I'll have an extra tool in the toolbox to pick an alternative no more than 90 degrees off my heading. And my aircraft glides at a 12:1 ratio. What is it for a 172, 7:1? And so on. My point is there is no single, cut-and-dried, be-all, end-all answer. Sometimes a mathematical equation can't encompass all the variables. It depends.

Engine failure numbers on GA aircraft are concerning, but look at all the poorly maintained crap out there, despite annual inspections and the best efforts of A&Ps. My personal powerplant is a 70 hr TTSN box-stock Lycoming IO-320-D1A that is religiously maintained...by me. So I like my chances of the prop continuing to turn on the climb-out. So I appreciate your input, but I will continue to...safely...climb to TPA at 90 KIAS.

 

[denverpilot]

I've seen more airplane engines killed due to excessive heat production than midairs, if you want to talk anecdotes.

Yes, but it wasn't anecdotal, I was speaking in hard numbers terms of what real risks are documented to happen the most often during takeoff. Fatal midairs on departure are a "wow!" event. Fatal engine loss of power events are nearly commonplace comparatively.

But the heat thing did leave SoCalFlyer an "out" from his original assertion that his shallow climb was primarily about mid airs, enough so that he has to exercise the "there were other considerations" clause below... Not that those considerations were important enough to mention first in the original post... Heh...

As I stated before, there are other considerations to the faster, shallower climb too, engine cooling being near the top of the list during our recent 105 F days. I prefer the better visibility in my own nontowered Wild West corner of airspace. Our standard pattern entry is left crosswind over the numbers (we're in a little fishmouth cutout of Ontario's Class C) so a very steep climb may blank out that NORDO Aeronca on crosswind. As for engine failure, at 90 KIAS I've got a boatload of extra kinetic energy (as you point out), and less of a forward push to establish best glide than I'd have at Vx or Vy...so maybe a little altitude saved in the transition. I've scouted my airport for possible engine-out landing sites, so if the engine decided to quit at the dreaded 350'-400' AGL, I'll have an extra tool in the toolbox to pick an alternative no more than 90 degrees off my heading. And my aircraft glides at a 12:1 ratio. What is it for a 172, 7:1? And so on. My point is there is no single, cut-and-dried, be-all, end-all answer. Sometimes a mathematical equation can't encompass all the variables. It depends.

Engine failure numbers on GA aircraft are concerning, but look at all the poorly maintained crap out there, despite annual inspections and the best efforts of A&Ps. My personal powerplant is a 70 hr TTSN box-stock Lycoming IO-320-D1A that is religiously maintained...by me. So I like my chances of the prop continuing to turn on the climb-out. So I appreciate your input, but I will continue to...safely...climb to TPA at 90 KIAS.

Summary:
- You want the nose lower in summertime.
- But it's still because of preference, and you still haven't done the math on what the real risk of that "Aeronca" being there are, versus the real risk of a loss of power.
- Engine failure numbers are concerning but new engines don't fail.
- Math might fail if I use the wrong assumptions, so I won't use it to see if one scenario is so far off the scale more common than another that the lesser one almost doesn't matter.



When it comes to takeoffs and aviation discipline, I sometimes understand why the airline guys chuckle at us lowly private pilots. Guess who doesn't launch without a concrete departure plan based not on "preference", but on hard won numerical knowledge of what's going to hurt the most often? The Part 121 folks.

It's not all about the "feels". Preference is great. One has to constantly ask if the preference is based on anything real.

Let's say it's wintertime now. We are back to:

36 seconds of risk of a rare NORDO inside the two degrees of visual coverage you can't see forward who also has to be on a collision course, after a long careful look at it prior to throttle up...

Compared to having a known departure profile and go/no-go point calculated for a safe return to the departure runway (adding whatever margins you like).

I never questioned the shallower climb for any operation that would exceed a known limit of the aircraft like temperature.

I asked if there were any numbers behind the "preference" to see forward vs the known numbers of loss of power accidents on departure.

I've argued the non-rational "feels right" stuff with an instructor who showed the math and his work on takeoffs many years ago, and saw the gross error in the use of emotion over rational numbers. It takes a while for it to sink in.

That your airport is a crosswind entry DID add a little bit of rationality to the decision, but I suspect there's very few NORDOs operating daily there.

Do you know that number? Do you climb at Vy at airports that don't have that as their norm? Do you climb harder in winter? If not, why not?

This is all intended to get people to think about planning takeoffs just like one plans the rest of the flight. It's not personal at all, you just happened to say the correct words to set off my "he might not be planning by real risks" meter.

The meter fell a notch at "crosswind entries" being common. It didn't move lower at all at "temperature", because if temperature was the limiting factor, that limitation only applies for about 1/4 of a year for most of us, peaking at about half a year if one flies in PHX.

 

[SoCal RV Flyer]

Denverpilot, you've wasted a lot of key strokes trying to convince me to alter my procedure, but I stand by my original arguments.

I've seen more airplane engines killed due to excessive heat production than midairs, if you want to talk anecdotes.

An excellent point. All those repeated Vy takeoffs can really cook an engine! In aircraft often unequipped with a CHT gauge.

 

[LongRoadBob]

Here you go.

https://www.pilotsofamerica.com/community/threads/enroute-climb.96958/#post-2107328

Ah...thanks so much Wrench! That was the one. It started as en route climb discussion but dipped into takeoff climb out also. I appreciate the help!

 

[iamtheari]

Here are my related questions about Vx and Vy. Do they depend only on density altitude or also on power setting? That is, does Vy stay the same when I pull back from takeoff to climb and later to cruise power, or does it change? (Obviously rate of climb will change due to amount of excess power available, but does the indicated airspeed where climb rate is maximized vary?)

Second, is there a formula to calculate Vx and Vy at a certain density altitude from known standard day sea level numbers or is it only possible by empirical results from test flying?

I can say that empirically the drop in Vy at altitude is noticeable after climbing to 12,000 with full tanks, an instructor, two bag lunches, and warm air in Wyoming earlier this week. But I would like to know the more precise numbers to use in the event I need a maximum-rate climb. ATC told us not to delay and I held my tongue rather than saying I wasn't trying to climb so slow.

 

[flyingron]

Vx/Vy don't change with power setting in any appreciable way. The reason power available isn't constant across airspeeds is small difference in propeller efficiency. Vy usually occurs pretty close to the low point of power required curve. Both the PA and PR curves slide consistently to the right with altitude. Yes, you can calculate the PA/PR. Nice article here: http://www.nar-associates.com/technical-flying/altitude/part1/altitude_part1_wide_screen.pdf

Vx sees less change because as the excess power (Vy) speed moves right it is countered by the fact that you're going faster and need to pitch up further to keep the angle steeper.

 

[denverpilot]

Denverpilot, you've wasted a lot of key strokes trying to convince me to alter my procedure, but I stand by my original arguments.

I don't consider pointing out this you're taking a risk order of magnitude higher than the one you're correcting for, to be wasted words at all.

Perhaps others will learn from them and make their choices by the numbers and not by emotions.

 

[SoCal RV Flyer]

Perhaps others will learn from them and make their choices by the numbers and not by emotions.

I'm simply taking all factors into account, and not blindly following a one-size-fits-all formula. I'm a sensitive guy, but emotional is a stretch.

 

[denverpilot]

I'm simply taking all factors into account, and not blindly following a one-size-fits-all formula. I'm a sensitive guy, but emotional is a stretch.

I was just going by your stated goal, that you "prefer" it. You never gave valid numbers for any other reason other than summertime heat. So with only that stated goal, that's emotion, not risk analysis.

 

[ircphoenix]

Really guys? Stop it.

I like both of you. And the dick measuring is nonsense. Leave that to Glenn and Tom-D.

 

[denverpilot]

Really guys? Stop it.

I like both of you. And the dick measuring is nonsense. Leave that to Glenn and Tom-D.

LOL. I'm not measuring anything, simply pointing out there's a mathematical error in the risk analysis. It's common with humans. See: Idiots stampeding at JFK because they heard metal poles hit the floor.

 

[ircphoenix]

LOL. I'm not measuring anything, simply pointing out there's a mathematical error in the risk analysis. It's common with humans. See: Idiots stampeding at JFK because they heard metal poles hit the floor.

If that were true, it would have been 1 additional post. SCRV is going to do it his way, despite your mathematical risk analysis. He has read your information, processed it, and decided that it doesn't work for his situation. Just as you have seen what his methods are, and decided you don't like his.

Fine. Okay. /end

 

[SoCal RV Flyer]

I think that we need to agree to disagree. If you want to talk hard facts, the number of arguments won on the internet, in its history, is precisely zero.

But I agree with Denverpilot that nothing is being measured here...just a healthy exchange of ideas. It's a forum, right?

 

[Joshuajayg]

To your specific post, it is the flight school checklist. It's a little unclear why it is that way. . . .

I'm aware of (at least theoretically) Vx but in the same checklist Vx is 63 KIAS.
When I asked about the checklist for take off climb out being 3 KIAS lower than Vy, he seemed to think it might be a mistake, and that maybe we should use 79 from now on. . . .

If you are not at sea level, chances are it is the best rate of climb for your elevation. Vy drops as altitude increases. Seems like a good reason considering the small change in published airspeed.

And if I am thinking correctly, your Vy might change with aircraft weight. I haven't read that anywhere and I am really just pulling it out of a hat.

Alright, I'll just go read to see if that is true.

 

[midlifeflyer]

If you are not at sea level, chances are it is the best rate of climb for your elevation. Vy drops as altitude increases. Seems like a good reason considering the small change in published airspeed.

And if I am thinking correctly, your Vy might change with aircraft weight. I haven't read that anywhere and I am really just pulling it out of a hat.

Alright, I'll just go read to see if that is true.

Let us know what you find (BTW, you are correct).

 

[Joshuajayg]

Let us know what you find (BTW, you are correct).

I couldn't find a direct answer using the FAA publications I have but I checked my 182 POH and as sure as day, weight has an affect on best rate and best angle climbs.

Since these numbers are based upon induced drag, parasitic drag, and thrust available, weight would obviously have an affect. With more weight, a higher angle of attack would be needed to produce the lift necessary to keep the aircraft aloft. With a higher angle of attack, induced drag increases. Therefore to reach the thrust/drag equilibrium necessary for either Vx or Vy, the airspeed with change with weight. Also, as altitude increases, Vx increases and Vy decreases until the aircraft reaches the point it can no longer climb.

Here's a page from the POH that has different Vy speeds for different weights.

 

[midlifeflyer]

I couldn't find a direct answer using the FAA publications I have but I checked my 182 POH and as sure as day, weight has an affect on best rate and best angle climbs.

Since these numbers are based upon induced drag, parasitic drag, and thrust available, weight would obviously have an affect. With more weight, a higher angle of attack would be needed to produce the lift necessary to keep the aircraft aloft. With a higher angle of attack, induced drag increases. Therefore to reach the thrust/drag equilibrium necessary for either Vx or Vy, the airspeed with change with weight. Also, as altitude increases, Vx increases and Vy decreases until the aircraft reaches the point it can no longer climb.

Here's a page from the POH that has different Vy speeds for different weights.

If you've come across the formula for calculating Va at different weights, it's the same one:

V1=V2 * Sq Root (W1/W2)

Where:
V1= Airspeed you want to calculate
V2=Published airspeed for max gross weight
W1=Weight for which airspeed is to be determined
W2=Gross weight for which airspeeds are published

It applies to all load-based airspeeds. You don't see it that much in many training aircraft (except for Va) because the range from minimum weight to maximum weight is small enough that it doesn't make that much of a difference.

 

[thebruce]

...just a healthy exchange of ideas. It's a forum, right?

It has been useful to me as a 100hr VFR-only ASEL guy. So thanks!