Departures: Vx, Vy, or Zoom

[Jay Honeck]

What, for asking a simple question?




Your aerodynamics aren't making sense. Are you stating that the airplane maintained a 45 degree up pitch maintaining 75 knots indefinitely? 1 minute? 5 minutes? From ground to 1000'?

I find it hard to believe an RV8 with a 180hp engine is capable of 45 degree sustained climb from take off roll to top of traffic pattern.

As far as my other comment:

Sorry, sometimes the truth hurts.

Read. For. Comprehension.

Go back to the first report, and see how long we held the 45 degree up angle before aborting. Report back when you fully understand.

 

[Velocity173]

I can do the same climb to 1,000 ft in my Glasair in 45 secs on only 160 HP. Yep...you bought the wrong plane.

 

[Jay Honeck]

Why don't you list the credentials and experience of those who support your half-asx theories with those who have pointed out the idiocy and see how they stack up?

Theories? I'm testing them in a real live aeroplane. What are YOU doing, besides throwing peanut shells, while watching Honey Boo Boo?

 

[wabower]

The physics element of the equation should include the density and location of the rocks and other obstacles that might be important to miss.

So what I learned in PPL training still holds:
Vx(best angle) is a slower speed which gives me the most altitude in the shortest distance traveled but takes longer to get there, and Vy(best rate) is a faster speed which gives me the most altitude in the fastest amount of time but requires a longer distance to get there. Any other speed is a compromise and provides an intermediate result. Vx is good for clearing an obstacle, but otherwise Vy is best because it gives you a better safety margin if your engine fails you.

The physics remains the same.

Did I mess it up.

 

[wabower]

Are you willing to perform the first part of that alleged 45-degree climb maneuver in the presence of witnesses?

Read. For. Comprehension.

Go back to the first report, and see how long we held the 45 degree up angle before aborting. Report back when you fully understand.

 

[Jay Honeck]

So what I learned in PPL training still holds:
Vx(best angle) is a slower speed which gives me the most altitude in the shortest distance traveled but takes longer to get there, and Vy(best rate) is a faster speed which gives me the most altitude in the fastest amount of time but requires a longer distance to get there. Any other speed is a compromise and provides an intermediate result. Vx is good for clearing an obstacle, but otherwise Vy is best because it gives you a better safety margin if your engine fails you.

The physics remains the same.

Did I mess it up.

Yup. But surprisingly (to me) the time to a specific altitude was virtually identical between a Vy climb and a zoom climb. More surprisingly yet, a Vx climb was at such a steep deck angle that neither of us felt comfortable enough to continue the test.

 

[RotorAndWing]

Read. For. Comprehension.

Go back to the first report, and see how long we held the 45 degree up angle before aborting. Report back when you fully understand.

Jay, I understand. In fact I understand aerodynamics much better than you could ever possibly dream of after reading your comments.

Again, 45 degree nose up from takeoff roll to traffic pattern attitude at 75 knots?? Uh uh, I ain't buying it.

I would agree you could get a 45 degree pitch momentarily during climb, but not sustained. Your airplane simply doesn't have the performance.

 

[Jay Honeck]

Did you fly VY corrected for weight?

Yew betcha.

 

[Jay Honeck]

Jay, I understand. In fact I understand aerodynamics much better than you could ever possibly dream of after reading your comments.

Again, 45 degree nose up from takeoff roll to traffic pattern attitude at 75 knots?? Uh uh, I ain't buying it.

I would agree you could get a 45 degree pitch momentarily during climb, but not sustained. Your airplane simply doesn't have the performance.

Good Lord.

Read. For. Comprehension. Go back to the original post, and see how long we held the 45 degree up angle before aborting. Report back when you get it.

 

[RotorAndWing]

Did you fly VY corrected for weight?

Yew betcha.

Please show us your calculation on that?

 

[Jay Honeck]

Please show us your calculation on that?

I will get right on that for you.

 

[skidoo]

So what I learned in PPL training still holds:
Vx(best angle) is a slower speed which gives me the most altitude in the shortest distance traveled but takes longer to get there, and Vy(best rate) is a faster speed which gives me the most altitude in the fastest amount of time but requires a longer distance to get there. Any other speed is a compromise and provides an intermediate result. Vx is good for clearing an obstacle, but otherwise Vy is best because it gives you a better safety margin if your engine fails you.

The physics remains the same.

Did I mess it up.

Sound good to me!

Now everyone consider these scenarios. Say one has a direct head wind of over 20 kts on takeoff. 1) airplane takes off and holds vx and ends up at 1000 ft at mid field. 2) airplane takes off and holds vy and ends up at the dep end of the runway at 1000 ft. 3) airplane takes off and holds some faster speed than vy and ends up 2000 ft beyond the dep end of the runway at 1000 ft.

Which of the three positions is better if the engine quits at 1000 ft?

I'm not suggesting that will or will not occur at the different speeds, nor that any particular one is better than the other, but wondering what others think if a particular aircraft did perform in such a way...

 

[RotorAndWing]

Good Lord.

Read. For. Comprehension. Go back to the original post, and see how long we held the 45 degree up angle before aborting. Report back when you get it.

Vy Climb at 75 knots. Within ten seconds, I aborted this departure when the deck angle exceeded 45 degrees up.

You alluded your aircraft is capable of sustaining a 45 degree pitch up, but you felt "uncomfortable". But in reality your airspeed was bleeding off, you left that little tidbit off.

If you did a correct Vy departure you would have never seen a 45 degree up pitch but a more comfortable lower pitch.

 

[RotorAndWing]

I will get right on that for you.

I won't hold my breath.

 

[Jay Honeck]

Sound good to me!

Now everyone consider these scenarios. Say one has a direct head wind of over 20 kts on takeoff. 1) airplane takes off and holds vx and ends up at 1000 ft at mid field. 2) airplane takes off and holds vy and ends up at the dep end of the runway at 1000 ft. 3) airplane takes off and holds some faster speed than vy and ends up 2000 ft beyond the dep end of the runway at 1000 ft.

Which of the three positions is better if the engine quits at 1000 ft?

I'm not suggesting that will or will not occur at the different speeds, nor that any particular one is better than the other, but wondering what others think if a particular aircraft did perform in such a way...

This is exactly the scenario I am testing. And we did have roughly a 20 knot headwind today, as we do most days on the coast.

IMHO, being over the runway environment when you hit 1000' gives you a better chance of making it back to the airport environment in the event of engine failure. Next time, we will note our position relative to the runway as we pass through 1000' with each technique.

 

[kgruber]

When IS the last time you actually flew? Do you really have no curiosity about this sort of thing? Is it that you resent those of us who can actually go out and test this stuff, or are you just naturally a curmudgeon?

Why are you on a piloting group again?

You have no idea of my experience or current flying. Just as you have little knowledge about aircraft performance. I love the part where you say holding a climb at 75knots is a 45° angle. You are clueless and should be 709'd.

 

[douglas393]

This is exactly the scenario I am testing. And we did have roughly a 20 knot headwind today, as we do most days on the coast.

IMHO, being over the runway environment when you hit 1000' gives you a better chance of making it back to the airport environment. Next time, we will note our position relative to the runway as we pass through 1000' with each technique.

Being a 1000 feet over the runway environment when the engine craps out is certainly better than being 500 feet over the runway environment, however, for me the issue is time. The engine dying in most circumstances I would think is a function of time and not altitude, and thus Vx will give you a lower altitude when the engine craps out than Vy, and in most circumstances that will be less safe.

 

[Jay Honeck]

You alluded your aircraft is capable of sustaining a 45 degree pitch up, but you felt "uncomfortable". But in reality your airspeed was bleeding off, you left that little tidbit off.

If you did a correct Vy departure you would have never seen a 45 degree up pitch but a more comfortable lower pitch.

That was the Vx departure. We had the terms reversed on our checklist, and in my original post. (I have since corrected this error.)

Left unsaid is that we later climbed to 2000' over an uninhabited island and tested the Vx climb again, just to see what that steep deck angle felt like while at a safer altitude. We were able to hold 75 knots pretty much indefinitely, at something less than a 45 degree up angle. I stopped the test at 3500' MSL.

I don't know the precise deck angle, but it was still way steeper than I would want to ever use in the airport environment, simply because we had zero forward visibility. Cooling would become an issue, too.

 

[wabower]

Does your attitude instrument have any horizontal lines inscribed on the surface of the moving part?

That was the Vx departure. We had the terms reversed on our checklist, and in my original post. (I have since corrected this error.)

Left unsaid is that we later climbed to 2000' over an uninhabited island and tested the Vx climb again, just to see what that steep deck angle felt like while at a safer altitude. We were able to hold 75 knots pretty much indefinitely, at something less than a 45 degree up angle. I stopped the test at 3500' MSL.

I don't know the precise deck angle, but it was still way steeper than I would want to ever use in the airport environment, simply because we had zero forward visibility. Cooling would become an issue, too.

 

[Jay Honeck]

Does your attitude instrument have any horizontal lines inscribed on the surface of the moving part?

You're still up?

Yeah, but I did not take note of it. I am arriving at the 45 degree estimate by asking my back seat copilot, who felt like she was BENEATH rather than behind me...

 

[RotorAndWing]

That was the Vx departure. We had the terms reversed on our checklist, and in my original post. (I have since corrected this error.)

Left unsaid is that we later climbed to 2000' over an uninhabited island and tested the Vx climb again, just to see what that steep deck angle felt like while at a safer altitude. We were able to hold 75 knots pretty much indefinitely, at something less than a 45 degree up angle. I stopped the test at 3500' MSL.

I don't know the precise deck angle, but it was still way steeper than I would want to ever use in the airport environment, simply because we had zero forward visibility. Cooling would become an issue, too.

So did you enter at 2000' at 75knots or less to simulate a takeoff? Are you saying that entering at 2000'/ 75 knots your airplane held the same pitch angle (something now less than 45 degrees) for 1500' (3500'agl)?

 

[RotorAndWing]

You're still up?

Yeah, but I did not take note of it. I am arriving at the 45 degree estimate by asking my back seat copilot, who felt like she was BENEATH rather than behind me...

Ah hah, now the truth comes out.

 

[moonshine]

Now if only we could somehow turn that runway into a conveyor belt....

 

[ronnieh]

He also needs to determine V1.

What does V1 have to do with a single engine airplane?

 

[Jay Honeck]

I won't hold my breath.

Good choice.

 

[Jay Honeck]

So did you enter at 2000' at 75knots or less to simulate a takeoff? Are you saying that entering at 2000'/ 75 knots your airplane held the same pitch angle (something now less than 45 degrees) for 1500' (3500'agl)?

There was initially an element of zoom to the climb. I was probably doing 130 knots at the start of the climb, but immediately reduced power to achieve 75 knots. I then went back to full power, adjusting pitch to maintain 75 knots.

1500' later, I was still grinding along at 75 knots, climbing at something around 1500 FPM. I basically aborted the test because I got bored with it, and had proved that the deck angle was excessive, to the point where we would never want to use a Vx departure near the runway environment.

 

[RotorAndWing]

Good choice.

Now that you have admitted you didn't use correct data, you didn't understand basic PP aerodynamic terminology, you "exaggerated" flight parameters I doubt seriously you really understand Vy (or any V speeds) and the correlation of weight, DA, temp, etc.

You are a prime example of why people are so skeptical of EAB.

 

[Jay Honeck]

For those student pilots who may be following this thread, it's important to note two things:

1. These tests are an exercise that I am doing for my own personal satisfaction, in my experimental RV-8A.

2. You should fully understand that a Vy climb will ALWAYS be "safer" at almost any point during the departure. You will always be farther away from cumulo-granite, at every point (except the final point) during the take-off procedure, by maintaining a Vy climb.

This has been a public service announcement.

 

[RotorAndWing]

There was initially an element of zoom to the climb. I was probably doing 130 knots at the start of the climb, but immediately reduced power to achieve 75 knots. I then went back to full power, adjusting pitch to maintain 75 knots.

So when you takeoff from a runway you accelerate to 130 knots, start the climb, reduce power to maintain 75 knots, then go back to full power??

This is why your "test" on takeoff and Vy speed is invalid. You did not replicate a true takeoff.

1500' later, I was still grinding along at 75 knots, climbing at something around 1500 FPM.

You are not accounting for the 130 knots previous to the climb that got you to the 1500' mark. Had you done a true takeoff with power and speed back to rotation speed, then applied full power and pitched for 75knots your outcome would have been much much less.

I basically aborted the test because I got bored with it, and had proved that the deck angle was excessive, to the point where we would never want to use a Vx departure near the runway environment.

Again, without performing the test accurately you proved nothing, nada zip.

Here's a novel idea. Go do a normal takeoff from the runway, pitch to Vx speed and climb to pattern attitude. You'll quickly find out it's not as extreme as you are attempting to make it out to be.

 

[Jay Honeck]

Now that you have admitted you didn't use correct data, you didn't understand basic PP aerodynamic terminology, you "exaggerated" flight parameters I doubt seriously you really understand Vy (or any V speeds) and the correlation of weight, DA, temp, etc.

You are a prime example of why people are so skeptical of EAB.

And you obviously have little comprehension of the topic.

This is a forum for open discussion, and the tossing around of ideas. I don't pretend to be a test pilot, or an aerodynamics expert, nor do I have any particular expertise in flying precise profiles for the purposes of comparison. These tests are imprecise because of these limitations, but they are the best we can do...for now.

I will improve, and over time I will explore the various corners of the RV-8's performance envelope. I share these experiences here for the benefit of all. Your non-productive bile and bitterness have no place here, and your rude posts say far more about you than you can comprehend.

Now go find something productive to do with your time. There's probably a good old movie on TCM.

 

[Jay Honeck]

So when you takeoff from a runway you accelerate to 130 knots, start the climb, reduce power to maintain 75 knots, then go back to full power??

This is why your "test" on takeoff and Vy speed is invalid. You did not replicate a true takeoff.

No, really? Why would you assume that I wanted to EXACTLY replicate a "true takeoff"? Or anything else, other than what I stated my goal to be, which was to replicate the DECK ANGLE of a Vx climb.

You are not accounting for the 130 knots previous to the climb that got you to the 1500' mark. Had you done a true takeoff with power and speed back to rotation speed, then applied full power and pitched for 75knots your outcome would have been much much less.

Much less what? Deck angle? That's silly talk. By the time I had climbed 1500 feet, the effects of the zoom were long since gone, and we were grinding along at a true Vx climb. And the deck angle was excessive to the point where we proved that we would NEVER want to use that departure technique close to terra firma.

Again, without performing the test accurately you proved nothing, nada zip.

Wrong again. I verified EXACTLY what I was trying to prove. There is no doubt.

Here's a novel idea. Go do a normal takeoff from the runway, pitch to Vx speed and climb to pattern attitude. You'll quickly find out it's not as extreme as you are attempting to make it out to be.

Wrong again. There is no way we would attempt a 75 knot climb out in the -8A, just a few feet off the ground. You are literally hanging on the prop, and any loss of power would be a bit too exciting for our tastes. Combine this with the zero forward visibility, and the lack of cooling air reaching the tightly cowled engine (especially in the 91 degree heat), and you've got a departure procedure that is not anything approaching safe.

 

[RotorAndWing]

This is a forum for open discussion, and the tossing around of ideas. I don't pretend to be a test pilot, or an aerodynamics expert, nor do I have any particular expertise in flying precise profiles for the purposes of comparison. These tests are imprecise because of these limitations, but they are the best we can do...for now.

In the beginning you were doing just that and belittling anyone who questioned you. Some even offered to correct your misunderstandings and you dug in even deeper.

Best you can do for now? C'mon, not even near being valid, just you playing with your airplane.

I will improve, and over time I will explore the various corners of the RV-8's performance envelope.

I predict you will become a NTSB report eventually.

I share these experiences here for the benefit of all.

And when someone disagrees, you go on the attack. Pitiful.

Your non-productive bile and bitterness have no place here, and your rude posts say far more about you than you can comprehend.

Rude? By pointing out your inconsistencies?

Once again, you have proved your "point" oh so well. But more importantly you have proved what many believe, and you are a prime example of why people are skeptical of EAB.

 

[redtail]

For those student pilots who may be following this thread, it's important to note two things:

1. These tests are an exercise that I am doing for my own personal satisfaction, in my experimental RV-8A.

2. You should fully understand that a Vy climb will ALWAYS be "safer" at almost any point during the departure. You will always be farther away from cumulo-granite, at every point (except the final point) during the take-off procedure, by maintaining a Vy climb.

This has been a public service announcement.

So unless I'm practicing for an airshow or there's a bandit on my six, a zoom climb gives me no real advantage over a normal Vy climb. Correct?

 

[RotorAndWing]

Wrong again. There is no way we would attempt a 75 knot climb out in the -8A, just a few feet off the ground. You are literally hanging on the prop, and any loss of power would be a bit too exciting for our tastes. Combine this with the zero forward visibility, and the lack of cooling air reaching the tightly cowled engine (especially in the 91 degree heat), and you've got a departure procedure that is not anything approaching safe.

kgruber was correct, you are an ideal candidate for a 44709 ride.

Go read the Private Pilot PTS. One of the task you must demonstrate is a Vx takeoff and climb then transition to a Vy climb.

 

[Jay Honeck]

You have no idea of my experience or current flying. Just as you have little knowledge about aircraft performance. I love the part where you say holding a climb at 75knots is a 45° angle. You are clueless and should be 709'd.

You really need to find another hobby. Your counterproductive bitterness and pointless posts truly have no place in POA, or aviation.

If you have something productive to contribute, please keep a civil tongue.

 

[Jay Honeck]

And when someone disagrees, you go on the attack. Pitiful.

I am never rude, until confronted by it. You, sir, have contributed precisely nothing to this conversation except to say that you don't like me.

Frankly, no one cares -- least of all me.

 

[Jay Honeck]

So unless I'm practicing for an airshow or there's a bandit on my six, a zoom climb gives me no real advantage over a normal Vy climb. Correct?

In theory, yes. Sadly, however, we did not record our location over the airport when we reached 1000' AGL using either method, which was a critical parameter to omit.

There is one possible point where a zoom climb MIGHT be "safer" than a "Vy climb -- and that's at its highest point. IF the zoom climb results in your ending up more directly over the airport environment upon reaching 1000' AGL, and the Vy climb does not, you should, in theory, have a better chance of making it back to the runway in the event of an engine failure at 1000' AGL by using a zoom climb.

Next time we will record our position over the airport when we reach 1000'. I suspect that the results will be very similar -- which should mean that there will be NO advantage of a zoom climb, other than the fun factor. But until I test it myself, I shan't say for certain.

Since you are always higher above the ground at any OTHER point during a Vy climb, this ultimately means that your chances of returning to the runway are better in the event of an engine failure. Since you've got 58 seconds at any other point in the climb, and only 2 seconds at the highest point, the safety tradeoff is not a good one.

So, at BEST, a zoom climb will only be "safer" at the highest point of the climb. During the REST of the climb, the Vy climb is always going to be "safer". In the end, the results will probably match what we all expect -- which is that a Vy climb will almost certainly always be safer.

The surprising part, to me, is that the TIME to climb between the two methods is virtually the same. (Just 2 seconds apart, in my test.) I did not expect that.

 

[Henning]

A real zoom climb you accelerate to the aircraft's maximum clean level speed in ground effect (or to the end of the runway) then pull 3Gs to the vertical until you get close to Vx then push the nose over to maintain Vx.

 

[NineThreeKilo]

You really need to find another hobby. Your counterproductive bitterness and pointless posts truly have no place in POA, or aviation.

If you have something productive to contribute, please keep a civil tongue.

How do you have two private pilots licenses at once??

 

[Jay Honeck]

A real zoom climb you accelerate to the aircraft's maximum clean level speed in ground effect (or to the end of the runway) then pull 3Gs to the vertical until you get close to Vx then push the nose over to maintain Vx.

Yeah, I didn't do that today. I used 120 knots, and a +1G pull. Although I did push the nose over to maintain Vy after the initial zoom.

A pre-zoom speed of closer to 140 knots works better. I will try that next time we run these tests.

I was just thinking about our error-laden checklist showing Vy (should be Vx) as 75 knots in the -8A, and I wonder how the original builder arrived at that number? Are they using the actual indicated airspeed in our aircraft, or is that some ideal number from Van's?

Given the extreme deck angle we experienced doing a Vx climb, I wonder if it's possible that number is bogus?

Hmmmmm. Something else to test.