Departures: Vx, Vy, or Zoom

[KSCessnaDriver]

Depends on what weight you are taking off at. At my typical flying weights, I would consider it depending on speed at failure and conditions ahead as I have performed tests that show me I still have reasonable ability to climb on a single engine, and indeed proved it out in another 310 years ago that considering I had over 7000 of runway left, I should have just landed ahead after failure right after rotation. Pt 23 doesn't make any requirements for SE climb nor does it require testing for any abilities below gross weight, that does not mean the performance doesn't exist. This is where multi engine flying is more complex than single engine, you have more options which requires more thought as to which option one should choose where along the path when something happens, and all this needs to be figured before the throttles go forward.

That's great, when it's your airplane and you can go out and test the thing. When you're flying somebody's airplane, you don't have the luxury of being able to go out and play with it. If I owned a piston twin, I'd probably play with it and see if I could come up with a reasonable V1 speed, but it's just not practical for anyone.

By all means, I'm not saying its wrong to have a V1 in a piston twin, it just doesn't make a whole lot of sense to me. The window from when you hit V1 to VR is extremely small.

 

[Henning]

In a Seneca you are in the air before you can continue SE, however if you have enough runway you can ensure that you still have enough ahead of you to land out if that failure occurs before you can fly away OEI.

How do you know? This factor is WEIGHT DEPENDENT. This is the factor SE pilots always seem to forget to consider when telling us how dangerous and useless our piston twins are. Ability to climb is a factor of excess HP. I can vary that factor by how I load my plane.

 

[gismo]

Yeah, I'm feeling the love.

Don't know about the love part but I do like you.

What makes you think that I won't fly conservatively? Because I actually went out and tested several different departure techniques?

I have learned many great things about my new aircraft since starting this thread:

1. I've learned, through actual flight testing, that a zoom climb is no safer than a Vy climb, nor does it get me to pattern altitude any quicker, even though it FEELS quicker.

True but rather understated. A zoom climb is truly "no safer" than Vy from liftoff and in fact a fair bit less safe in most cases. It's also against FAR 91.303 although I've never heard of anyone getting in trouble for doing this.

2. I have determined through actual flight testing that a Vx departure climb in an -8 is uncomfortable to the point where we simply won't do them for anything short of necessity.

It won't be anywhere near as "uncomfortable" when you need it, i.e. with a high DA, high GW combination on a runway of "adequate" length. With high DA and high weight your deck angle will be considerably less because the climb gradient will be lower (same AoA). A Vx climb is a tool that should be applied when appropriate but not something that should be SOP.

3. I have learned, through actual flight testing, that it takes one minute to get to pattern altitude in the -8, on a 90+ degree day at sea level, which frankly surprised me. Apparently the excitement of flying the plane results in perceived time compression, because I would have swore that it was about 30 seconds before actually timing it with a stopwatch.

It's amazing how poorly our senses are at measurement, especially WRT time and when things get "exciting". It's no wonder that eyewitness accounts are usually extremely inaccurate.

With regard to POA, I have also learned many things:

1. I have learned that some of the posters here who know so much about aviation are incapable of imparting that wisdom to others without cruelty and sarcasm. As God's gift to aviation, they believe that subjecting oneself to their abuse is a fair trade in exchange for their knowledge.

There's some of that but to be fair some of the "cruelty" comes from the frustration of not being able to convince less experienced aviators that they should heed or at least give serious consideration to the advice given and the concern over the potentially serious consequences for ignoring it. I'm pretty certain that's a big factor in Bruce's rather enthusiastic comments on this thread. His opinions on aviation safety issues have a deep foundation and are correct way more often than not even if he sometimes gets carried away on the delivery. Think of this as "tough love" and it might be easier to swallow.

2. I have learned (for the thousandth time) that arguing with trolls only makes them happier and more persistent. After 20+ years in piloting groups, you would think I would remember this -- but it's like tequila. Every year or two, I have tie one on to remind myself why NOT to drink it.

I have a similar problem with chocolate chip cookies and sweets in general. But WRT my interactions on web forums I have a few "rules" that have served me well:
1) If I haven't gotten my point across in three tries the fourth isn't going to be any more successful and it's time to agree to disagree.
2) I try hard to avoid name calling and if I'm the recipient of such that usually terminates my interest in offering any further advice to the sender.
3) I prefer to assume that most folks here are nice persons in general and deserve to be treated as such even if they occasionally do or write something I don't like.
4) Last but not least by a long shot, when there's a disagreement I recognize that my opinion could be wrong no matter how firmly I believe in it.[/QUOTE]

 

[Skylane81E]

How do you know? This factor is WEIGHT DEPENDENT. This is the factor SE pilots always seem to forget to consider when telling us how dangerous and useless our piston twins are. Ability to climb is a factor of excess HP. I can vary that factor by how I load my plane.

Because a Seneca (being on the smaller side of twins) doesn't really haul all that much. Odds of being loaded such that you can give up 80% of your performance and fly away at rotation speed (or accelerate to it) ain't grand.

Besides that the thing flies off WAY under VMC. Doing my demos even with no rudder blocking from the MEI and with two folks and about half gas I never got near rotation speed before loosing directional control. I suppose I could reduce power on the good engine, but considering I was making ~200fpm at full power that doesn't seem like a good idea either. I'll just cut power and apply maximum brakes.

 

[denverpilot]

It doesn't. I'm just saying that piston twins and single engine climb are not a place I want to be.



That's great. Unfortunately, as a professional, I don't get a choice on how much cargo goes on my piston twin. I'm paid to fly the airplane to its fullest extent, not pussyfoot around trying to make it safer by limiting the usefulness of the aircraft. So I fly it as the book and company opspecs say to fly it. Engine failure before rotation, we ain't flying.

Understood. Your employer doesn't value your life as much as they value making a profit. A common theme in many businesses.

An owner can decide to fly differently, and probably should. Isn't enough airplane to do the mission safely? Buy a bigger one.

Doc posted a while who how did the numbers for determining a safe missed approach point at KASE for his aircraft to be able to climb back to at least MOCA with OEI. I was impressed with that, having seen plenty of crunched aluminum in the mountains here. It included a limited load.

If your employer dispatched you to KASE they'd take the risk that you'd not be the next ball o' tin and blood.

I'm not judging it. It's just the truth.

 

[KSCessnaDriver]

Understood. Your employer doesn't value your life as much as they value making a profit. A common theme in many businesses.

An owner can decide to fly differently, and probably should. Isn't enough airplane to do the mission safely? Buy a bigger one.

Doc posted a while who how did the numbers for determining a safe missed approach point at KASE for his aircraft to be able to climb back to at least MOCA with OEI. I was impressed with that, having seen plenty of crunched aluminum in the mountains here. It included a limited load.

If your employer dispatched you to KASE they'd take the risk that you'd not be the next ball o' tin and blood.

I'm not judging it. It's just the truth.

If they were made to make it mandatory to operate a piston twin using V1 and V2 speeds, my gut tells me that there wouldn't be money to be made, simply because of how much below MTOW you have to be. So, it's simple, engine failure on the runway, abort. There's a 6 knot gap between VR and VYSE, and that gap gets closed in about 2 seconds. Doesn't bother me one bit.

And if it did, nobody is holding a gun to my head to make me do the job. It's an acceptable risk to take, IMO.

 

[ElPaso Pilot]

The window from when you hit V1 to VR is extremely small.

Are you sure about that??? Ask someone flying at GW, out of a short strip, or high DA if they agree with you (assuming they comprehend the concept ).

And when tooling along in ground effect at 140 knots near the departure end of the runway, thinking about why it might be important (or different) is a great exercise in understanding your own judgement, even in a piston single.

 

[KSCessnaDriver]

Are you sure about that??? Ask someone flying at GW, out of a short strip, or high DA if they agree with you (assuming they comprehend the concept ).

Sure, but on an ordinary takeoff, they aren't going to be very far apart on a piston twin. I'd like to hear the Doc's numbers for V1 and VR for his Seneca, just out of curiosity. I'm familiar with operating a piston twin at DA's above 9000ft.

 

[Jay Honeck]

4) Last but not least by a long shot, when there's a disagreement I recognize that my opinion could be wrong no matter how firmly I believe in it.

I always come here expecting to learn something, and a spirited debate. I was proved wrong on several points early on, and it was all good.

What bothers -- and, frankly, worries -- me about some of the posters in this thread is how they characterized my relatively simple flight testing as "unsafe".

Say and think what you will about my relative experience level, but after twenty years of flying a couple of times per week, and six weeks of intensive, daily transition flight training, practicing zoom climbs, Vx departures, and Vy departures is neither unsafe or even particularly challenging.

I frankly worry about the proficiency of any pilot who portrays any of this as particularly challenging, let alone unsafe. For those who truly believe any of these departure techniques are unsafe, I suggest practicing them with your CFI at your next biennial flight review. They are fun, educational, and -- as with all flight training -- will certainly make you a better pilot.

 

[X3 Skier]

I always come here expecting to learn something, and a spirited debate. I was proved wrong on several points early on, and it was all good.

What bothers -- and, frankly, worries -- me about some of the posters in this thread is how they characterized my relatively simple flight testing as "unsafe".

I frankly worry about the proficiency of any pilot who portrays any of this as particularly challenging, let alone unsafe. For those who truly believe any of these departure techniques are unsafe, I suggest practicing them with your CFI at your next biennial flight review. They are fun, educational, and -- as with all flight training -- will certainly make you a better pilot.

I for one, encourage exploring the capabilities of one's aircraft and piloting skills but never in close proximity to the ground.

Cheers

 

[Jay Honeck]

I for one, encourage exploring the capabilities of one's aircraft and piloting skills but never in close proximity to the ground.

Cheers

I agree -- but every departure starts out close to the ground, dag-nabbit...

 

[Dr. O]

In honor of this ****in contest I did a max effort takeoff today in Fat Albert - a clapped out 1957 Apache with 6000 hour engines.
About 65 gallons of fuel. One person in the fat boy . Temp was 70 degrees. Field is at 610 feet. Low humidity (don't know the number - roughly 70%) 8-10 mph direct crosswind (the only way I know how to TOL)
Raised the nose at 65 (mph - the fat boy does not speak in knots). The upwind main lifted at roughly 850 feet from throttles forward and about 72 mph..
V1 does not exist on a 5000 foot runway for this plane as you will always be able to abort at Vr and still get stopped.
Vx does not exist (except in the minds of some) because Blue Line is higher - and I like living.
Parenthetic note: If you have never dumped an engine for real while well below Vmc (max effort turning climb), you haven't a clue. I have.
I have the clue. And I intend to never do it again.
So at 10 feet I lowered the nose a bit and let the go meter rotate clockwise a ways.
Raised the gear.
And then I ZOOMED.
And what did I prove?

Not a damned thing - but it sure was fun!

 

[denverpilot]

I always come here expecting to learn something, and a spirited debate. I was proved wrong on several points early on, and it was all good.

What bothers -- and, frankly, worries -- me about some of the posters in this thread is how they characterized my relatively simple flight testing as "unsafe".

Say and think what you will about my relative experience level, but after twenty years of flying a couple of times per week, and six weeks of intensive, daily transition flight training, practicing zoom climbs, Vx departures, and Vy departures is neither unsafe or even particularly challenging.

I frankly worry about the proficiency of any pilot who portrays any of this as particularly challenging, let alone unsafe. For those who truly believe any of these departure techniques are unsafe, I suggest practicing them with your CFI at your next biennial flight review. They are fun, educational, and -- as with all flight training -- will certainly make you a better pilot.

Reading back through the threads, it was you who started by saying flatly without a shred of aerodynamic knowledge that the zoom maneuver was SAFER (it wasn't posed as any sort of " learning question " either), and numerous people refuting same.

No one started calling you "unsafe" until you continued to argue the point. And that was probably predicated on invincibility attitude more than the original false thesis.

 

[N801BH]

I agree -- but every departure starts out close to the ground, dag-nabbit...

AND...... Every landing too............

 

[gismo]

AND...... Every landing too............

Last time I landed a floatplane I was a long ways (relatively speaking) from the ground the whole time.

 

[Henning]

AND...... Every landing too............

Dude, could you imagine the look on Jay's face doing a Vx take off in your plane? Talk about extreme deck angles, not to mention not having enough right rudder to keep the plane from turning left and no fwd visibility.

 

[Skylane81E]

Understood. Your employer doesn't value your life as much as they value making a profit. A common theme in many businesses.

More just a fact of life with many piston twins, VR comes before VMC so there is a short time where you are flying but can't continue OEI.
The good news is:
1: that window is often very small
2: VR isn't terribly fast in many of these planes meaning you don't need miles of runway ahead to stop, especially considering that they sort of fall out of the sky without power.

So loosing an engine before you can fly away doesn't mean you will crash, even if you are already in the air, IF you have enough runway ahead. If not, well IMO better to go off the end relatively slow than to VMC roll in trying to push a departure with too little speed.

 

[bbchien]

Reading back through the threads, it was you who started by saying flatly without a shred of aerodynamic knowledge that the zoom maneuver was SAFER (it wasn't posed as any sort of " learning question " either), and numerous people refuting same.

No one started calling you "unsafe" until you continued to argue the point. And that was probably predicated on invincibility attitude more than the original false thesis.

THIS.

 

[denverpilot]

More just a fact of life with many piston twins, VR comes before VMC so there is a short time where you are flying but can't continue OEI.
The good news is:
1: that window is often very small
2: VR isn't terribly fast in many of these planes meaning you don't need miles of runway ahead to stop, especially considering that they sort of fall out of the sky without power.

So loosing an engine before you can fly away doesn't mean you will crash, even if you are already in the air, IF you have enough runway ahead. If not, well IMO better to go off the end relatively slow than to VMC roll in trying to push a departure with too little speed.

Completely understand. Doesn't change the observation. There's better aircraft that have better performance, but they can't make a profit operating them.

Aviation businesses have always been a compromise between making money and safety.

 

[bbchien]

Not to derail the thread, but I'm not exactly sure how you're defining V1 in a piston twin. Are you seriously saying that above a certain speed, on the runway, with an engine failure, you'll continue?

I can't find where I said any such thing. Point it out to me, okay? WHERE?

No. You determine V1. If it is greater than V2, you have the option to stop if you fail in ground effect at Vyse (v2) which is below V1. Otherwise at full gross you WILL stop, in the fence.

If V1 is less than V2, well you're sort of committed to take the fence, when the fail comes at V2, aren't you now?

 

[Skylane81E]

Doc, I'm in nonviolent agreement with you.

The ink may still be wet on my MEL, but as such I'd bet that nearly half my time in twins has been OEI

 

[KSCessnaDriver]

I can't find where I said any such thing. Point it out to me, okay? WHERE?

No. You determine V1. If it is greater than V2, you have the option to stop if you fail in ground effect at Vyse (v2) which is below V1. Otherwise at full gross you WILL stop, in the fence.

If V1 is less than V2, well you're sort of committed to take the fence, when the fail comes at V2, aren't you now?

Fair enough. I don't want to get in an huge deal about this, so I'll take your answer and move on.

 

[Jay Honeck]

Fair enough. I don't want to get in an huge deal about this, so I'll take your answer and move on.

Wait, you can't just back out of the debate. The good doctor must flog you some more before the conversation is allowed to reach that point!

 

[KSCessnaDriver]

Wait, you can't just back out of the debate. The good doctor must flog you some more before the conversation is allowed to reach that point!

I have neither the time nor the desire to get in the concept of using V1 and V2 in an airplane that they aren't published.

 

[Capt. Geoffrey Thorpe]

OK, just got back from the airport.


I have to assume that a zoom climb in an RV whatever with an IO-540 is more impressive than my rag and tube LSA with an 80 hp Rotax.

But, the nose is well above the horizon at Vx or Vy.

 

[Henning]

Having watched some of your videos, I see where the misconception of your Vx angle comes from, Mary sits below you when straight and level.

 

[Jay Honeck]

Having watched some of your videos, I see where the misconception of your Vx angle comes from, Mary sits below you when straight and level.

Haw! I'm telling.

Sent from my Samsung Galaxy S3...

 

[Ted]

OK, just got back from the airport.


I have to assume that a zoom climb in an RV whatever with an IO-540 is more impressive than my rag and tube LSA with an 80 hp Rotax.

But, the nose is well above the horizon at Vx or Vy.

Wait, you're telling me a 300 HP little plane performs better than an 80 HP little plane?

You must be an engineer.

 

[flyingcheesehead]

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.

Think about how you're adding energy to the system - In both cases, you're using the same engine, same hp, so after the same amount of time (assuming the same throttle settings), you will have added the same amount of energy to the system.

The minor difference in time can be traced to the differences in drag. Presumably, Vy is fairly close to Vg (and Ldmax) in the RV as it is in most birds. So, your Vy climb has more induced drag vs. the zoom climb throughout the maneuver with the exception of the pull part of the zoom, but it's a relatively small amount. In addition, your parasite drag at Vy will be lower for the majority of the maneuver. In the zoom climb, you'll have less induced drag except for the >1G portion, but you'll have a lot more parasite drag once you've accelerated through Vy. That is why the zoom climb took a couple of seconds longer - You were losing more of your energy to drag in the test window.

 

[flyingcheesehead]

What bothers -- and, frankly, worries -- me about some of the posters in this thread is how they characterized my relatively simple flight testing as "unsafe".

Say and think what you will about my relative experience level, but after twenty years of flying a couple of times per week, and six weeks of intensive, daily transition flight training, practicing zoom climbs, Vx departures, and Vy departures is neither unsafe or even particularly challenging.

I frankly worry about the proficiency of any pilot who portrays any of this as particularly challenging, let alone unsafe.

Jay,

No matter how much experience you have, a zoom climb in a single is less safe than Vy due to the higher time where your altitude/airspeed/energy profile leaves you in a bad situation in the event of an engine failure. It has nothing to do with pilot skill, and everything to do with physics and the potential for mechanical failure at a bad time. When you fly a zoom-climb profile, from a point in time very shortly after you accelerate through Vy until pretty much the point that you arrive at TPA back near Vy, you're in a worse situation that you would have been with a Vy climb.

Stop taking the criticisms as a knock on your stick-and-rudder skills and your experience. Even Bob Hoover is less safe in a zoom climb than a Vy climb.

 

[Jay Honeck]

Funny. I conceded that point on or about page two? But feel free to keep resetting the piñata!

 

[flyingcheesehead]

Funny. I conceded that point on or about page two? But feel free to keep resetting the piñata!

You conceded the point, yes - But you didn't concede the fight.

And, y'know, I like candy. And/or I wanted to give the mods another chance to close the thread.

 

[Jay Honeck]

You conceded the point, yes - But you didn't concede the fight.

And, y'know, I like candy. And/or I wanted to give the mods another chance to close the thread.

Let's see...a post where I specifically said "I was wrong" is SOMEWHERE in this thread...