Departures: Vx, Vy, or Zoom

[Henning]

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.

I think you haven't been in a real high performance plane before which is why you think the deck angle was so unbelievably steep, it also makes me believe you haven't done any power on stalls in your RV yet which you should have done long before these climb tests.

 

[Jay Honeck]

I think you haven't been in a real high performance plane before which is why you think the deck angle was so unbelievably steep, it also makes me believe you haven't done any power on stalls in your RV yet which you should have done long before these climb tests.

Well, you just joined the long line of trolls in this thread.

We did extensive power on, and power off stall training during transition to the -8. The deck up angle during a power on stall is extreme.

 

[Henning]

Well, you just joined the long line of trolls in this thread.

We did extensive power on, and power off stall training during transition to the -8. The deck up angle during a power on stall is extreme.

The deck up angle at Vx is less, so why did it scare you? If you know where it stalls, you should be perfectly comfortable right next to that, if not, practice slow flight until you are. You should not be uncomfortable for any reason flying your plane at Vx to pattern altitude and beyond. I'm not being a troll, just wondering why a Vx climb makes you so uncomfortable. Vx is well above stall speed.

 

[redtail]

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.

Yeah I was practicing the "impossible turn" (at altitude) with a 45° bank, during my flight review last week. Really enjoyed the experience.

I'm ok with Vx, but I always wonder if I'd be able to get the nose over quick enough from that pitch attitude!

I feel safest at Vy.

 

[Jay Honeck]

The deck up angle at Vx is less, so why did it scare you? If you know where it stalls, you should be perfectly comfortable right next to that, if not, practice slow flight until you are. You should not be uncomfortable for any reason flying your plane at Vx to pattern altitude and beyond. I'm not being a troll, just wondering why a Vx climb makes you so uncomfortable. Vx is well above stall speed.

I just spent a few minutes noodling around Google, trying to find some exact deck angle statistics for an RV-8 at Vx. Everyone, without exception, calls the deck angle "extreme", and there are many article echoing my opinion that no one in their right mind would climb out at Vx in an -8.

You have zero forward visibility. You have compromised cooling, which is already marginal in 90+ degree heat. And you have a condition that, should the engine sputter or stall, you could snap into a stall pretty quickly. There just isn't any plus side to using Vx, unless you have to clear some enormous obstacle at the end of the runway.

Personally, I would turn.

 

[Jay Honeck]

Yeah I was practicing the "impossible turn" (at altitude) with a 45° bank, during my flight review last week. Really enjoyed the experience.

I'm ok with Vx, but I always wonder if I'd be able to get the nose over quick enough from that pitch attitude!

I feel safest at Vy.

Vx in our Warrior and Pathfinder was steep, but not extreme. In the -8, it's positively scary. I would not use it unless some extreme need arose.

The -8 has so much excess power (for its weight) that there is no problem getting off a short field quickly -- even if you ignore V speeds entirely and just let it fly off the runway. We're off in 1000' or less every time.

And landings are just as short. During transition training, we practiced power off spot landings from 6500' over the airport. In addition to being great fun, I learned how to plop the -8 on a dime, if needed.

(Cue the "That's not safe, either!" peanut gallery! )

 

[flyingron]

Vy or faster. Altitude (over time) is your friend. Treating your engine nice by keeping the temperatures down lessens the chances you'll need to make use of that altitude in an emergency. Keeping the nose down increases visibility (of course, we know Jay doesn't look out the windows when flying, relying on everybody else to tell him where they are).

 

[Bill]

Can you say that three times in rapid succession?

Thatthatthat

 

[Skylane81E]

Here is the thing Jay, at light weights Atlas likely had every bit the excess power of the RV, I've run the numbers and with two folks and some gas my 182 matches the RV very well power to weight wise, plus a cambered leading edge and slotted fowler flaps. A solo maximum short field take off is an elevator ride.


Weeee!

 

[Matthew]

Yes, but oh, how Gruber will pout and whine, along with his buddy Bower! I would hate to aggravate them so by actually FLYING!

Alas, I'm done flying now till Sunday -- when we go up with our aerobatics instructor. I can't WAIT to hear the grounded kiwis here whine and moan when I post about THAT experience!

Well, for some of us it's our version of tough love.

I haven't found a way to download GPS tracks from the Nexus, but maybe you can borrow a 496? You should be able to import tracks into Google Earth and see the 3D results. You can then overlay the tracks and see a side-by-side-by-side representation of Vx, Vy, and zoom.

Right now you are your own test pilot, and that's fine. You are doing what plenty of others have done under more controlled conditions, and published Vx and Vy values are a result of those tests. Other speeds are compromises. Don't come to any conclusions yet about what's best until you have more complete data.

Use your aerobatics instructor this weekend and try a few things.

And try not to have too much fun.

 

[Bill]

-- when we go up with our aerobatics instructor. I can't WAIT to hear the grounded kiwis here whine and moan when I post about THAT experience!

Up with an instructor is great, you'll safely learn the your plane.

 

[steingar]

Jay, I stick to what I said. You're a man now, you can do as you like within limits. Mary is a grown woman and no doubt a competent pilot, so she knows enough to make an informed decision to go with you. Do whatever you like. I don't care. Just stop trying to convince the rest of us just how smart you are. In case you haven't noticed, it isn't working.

 

[Cap'n Jack]

I just spent a few minutes noodling around Google, trying to find some exact deck angle statistics for an RV-8 at Vx. Everyone, without exception, calls the deck angle "extreme", and there are many article echoing my opinion that no one in their right mind would climb out at Vx in an -8.

You have zero forward visibility. You have compromised cooling, which is already marginal in 90+ degree heat. And you have a condition that, should the engine sputter or stall, you could snap into a stall pretty quickly. There just isn't any plus side to using Vx, unless you have to clear some enormous obstacle at the end of the runway.

Personally, I would turn.

Jay- for getting improved data, a logging GPS would be helpful. A Bad Elf GPS Pro would work well, it can log up to 10 Hz, which should be adequate resolution for this experiment. Runs on it's own battery, so it can be placed where it can get a good signal, has a lot of track storage capacity. It will let you concentrate on flying and log the data for reduction at home.

You can then share the GPX files and prove your claims.

 

[bbchien]

Sigh.
Now we're being called trolls.
"Ya think it's the rest of the herd?"

 

[ronnieh]

Whew!!, tough crowd Jay. I still trying to figure out what V1 has to do with this thread. Perhaps just tongue in cheek sarcasm?

 

[wabower]

What is the definition of V1?

Whew!!, tough crowd Jay. I still trying to figure out what V1 has to do with this thread. Perhaps just tongue in cheek sarcasm?

 

[ronnieh]

Wayne, I do not have any type ratings but, I think it is the minimum speed which you can experience an engine failure and continue a take off. Sometimes it is referred to as decision speed, though I think this is in some ways a misnomer. This brings in the concept of a balanced field, ie a runway long enough to reach V1 and stop without running off the runway. Is this even close? If so my question remains...

 

[flyingron]

What is the definition of V1?

The point where you can continue the takeoff if a single engine fails. Since Jay's flying an RV-8 (and he declined my suggestion of putting the Apache engines on it to make it a twin), it's rather pointless.

 

[ronnieh]

So the suggestion made earlier to Jay to determine V1 has no bearing to this discussion?

 

[jhausch]

I think there is one set of data missing from your stopwatch timings. You also need distance so you can compare Vx to Vy to zoom in that axis, too.

When you start/stop the timer, you need the mark the distance traveled.

+1...

 

[Cap'n Jack]

I think there is one set of data missing from your stopwatch timings. You also need distance so you can compare Vx to Vy to zoom in that axis, too.

When you start/stop the timer, you need the mark the distance traveled.

+1...

That's why I suggested the use of the GPS logger. He can reduce the data to get his times, distances, and even climb angle (not pitch attitude though, needs something other than a GPS loggar for this. We also know he'll only get speed over the ground too)

 

[wabower]

Check the FAR/AIM definition #1 and report your findings.

The point where you can continue the takeoff if a single engine fails. Since Jay's flying an RV-8 (and he declined my suggestion of putting the Apache engines on it to make it a twin), it's rather pointless.

 

[RoscoeT]

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.

Of course you would abort. You would have eventually stalled if you continued to hold a 45 degree attitude. Not sure the point of your original 45 degree statement. A mighty Cherokeee 140 can hold 45 degrees for an amount of time as well.

 

[wabower]

The initially-alleged 45 degree angle has now been softened to "well, it felt pretty steep in the back seat" which is much more credible.

Of course you would abort. You would have eventually stalled if you continued to hold a 45 degree attitude. Not sure the point of your original 45 degree statement. A mighty Cherokeee 140 can hold 45 degrees for an amount of time as well.

 

[ronnieh]

Ah, Wayne I think I may get what you mean. V1 can be the maximum speed in the TO in which a pilot must take the first action (brakes, thrust reverse and so forth) to stop the airplane in the accelerate stop distance. Is this what you refer to? I still do not see how this applies to this thread. There is no data to calculate that speed is there? Each flight depending on weight and atmospheric conditions would have a unique V1. I THOUGHT these charts were just included in turbojet and planes that require a type rating? So are you saying Jay needs to know the runway length he needs to stop after reaching V1 even though no V1 exists for his plane? I still don't get how it applies.

 

[RoscoeT]

I just spent a few minutes noodling around Google, trying to find some exact deck angle statistics for an RV-8 at Vx. Everyone, without exception, calls the deck angle "extreme", and there are many article echoing my opinion that no one in their right mind would climb out at Vx in an -8.

Complete and utter horse hockey. I've owned an RV. I've flown most of the models, including the RV8. I've climbed at Vx. I've flown all the Pitts models. I've climbed those at Vx. You seem to think the RV is a 350 hp MX. It's not a great idea in these ultra high performance airplanes to climb at Vx ASAP immediately after breaking ground due to the very high deck angle, which may box you into in situation from which you cannot recover if your engine quits on low climbout. That is accepted among pilots of these types of ships. The RV is simply not nearly as extreme as you think. I know lots of RV pilots. I've got hundreds of hours in an RV4. The RV8 handles like a boat in comparison. I've never heard of this "nobody in their right mind would climb at Vx" bullsh!t. But maybe I need to read more "articles" rather than actually flying.

 

[wabower]

Meet me at Honeck's airport for the demo. Here's how we'll do it.

You will accelerate an RV-whatever from a standing stop, rotate when it will fly and then maintain 6' altitude as long as you want before starting the zoom. I will hold a remote engine-kill switch that I will activate no later than the time at which you start your zoom. Your job is to get it stopped on the remaining runway. Bring whatever you want to bet in small unmarked.

Ah, Wayne I think I may get what you mean. V1 can be the maximum speed in the TO in which a pilot must take the first action (brakes, thrust reverse and so forth) to stop the airplane in the accelerate stop distance. Is this what you refer to? I still do not see how this applies to this thread. There is no data to calculate that speed is there? Each flight depending on weight and atmospheric conditions would have a unique V1. I THOUGHT these charts were just included in turbojet and planes that require a type rating? So are you saying Jay needs to know the runway length he needs to stop after reaching V1 even though no V1 exists for his plane? I still don't get how it applies.

 

[wabower]

Maybe we could ask Honeck's acro instructor to duplicate and verify some of his "research."

Complete and utter horse hockey. I've owned an RV. I've flown most of the models, including the RV8. I've climbed at Vx. I've flown all the Pitts models. I've climbed those at Vx. You seem to think the RV is a 350 hp MX. It's not a great idea in these ultra high performance airplanes to climb at Vx ASAP immediately after breaking ground due to the very high deck angle, which may box you into in situation from which you cannot recover if your engine quits on low climbout. That is accepted among pilots of these types of ships. The RV is simply not nearly as extreme as you think. I know lots of RV pilots. I've got hundreds of hours in an RV4. The RV8 handles like a boat in comparison. I've never heard of this "nobody in their right mind would climb at Vx" bullsh!t. But maybe I need to read more "articles" rather than actually flying.

 

[ronnieh]

Wayne, I guess I am just to dumb to get what you are talking about. I am just trying to figure out how a non existent number (V1) for this aircraft relates to this thread. I certainly agree that in your scenario you will not get it stopped. In fact I agree with the general consensus regarding the fallacy of Jay's original assumption. I just don't understand the V1 tie in.

 

[wabower]

Did you read the definition? Which part is causing you trouble? V1 is clearly and existent number, whether or not it's published. If a pilot intends to operate his plane in a manner that causes the number to come into play, shouldn't he be required to know it?

As Bruce mentioned, he has done extensive research in his Seneca to determine speeds and weights that are critical to know, but that Piper didn't see fit to publish, for the same reasons most other manufacturers elected to omit them. FYI, the reasons were because they weren't required to do so for planes less than 6,0000# GW, and the information could have created a negative impact on sales.

Wayne, I guess I am just to dumb to get what you are talking about. I am just trying to figure out how a non existent number (V1) for this aircraft relates to this thread. I certainly agree that in your scenario you will not get it stopped. In fact I agree with the general consensus regarding the fallacy of Jay's original assumption. I just don't understand the V1 tie in.

 

[ronnieh]

Now I understand. I thought it was being said that he should know what the published V1 is for his plane in different configurations. What Bruce meant was Jay should experiment to determine how much runway he needs especially doing the so called zoom. Excuse my ignorance, makes more sense now. And yes Jay should determine these speeds if he is going to operate in these realms. I of course was thinking of the definition of losing an engine and continuing the TO. My bad. Thanks.

 

[ja_user]

Now I understand. I thought it was being said that he should know what the published V1 is for his plane in different configurations. What Bruce meant was Jay should experiment to determine how much runway he needs especially doing the so called zoom. Excuse my ignorance, makes more sense now. And yes Jay should determine these speeds if he is going to operate in these realms. I of course was thinking of the definition of losing an engine and continuing the TO. My bad. Thanks.

Its is very useful to know how much runway you need to stop (based upon your current speed.) There is a point on the runway that you cannot safely land any longer, and would overrun. As speed increases the distance required increases. So that can be an issue if you are doing 120-140mph in a slick aircraft with 1000ft remaining of runway.

 

[Capt. Geoffrey Thorpe]

Vp = 6.53 posts per hour.

 

[Jay Honeck]

Jay, I stick to what I said. You're a man now, you can do as you like within limits. Mary is a grown woman and no doubt a competent pilot, so she knows enough to make an informed decision to go with you. Do whatever you like. I don't care. Just stop trying to convince the rest of us just how smart you are. In case you haven't noticed, it isn't working.

Never tried to convince anyone of my intellect. Frankly, I don't really care what you think about me personally, in case you haven't noticed (!), but I do enjoy the learning experience of interacting with other pilots.

What I don't enjoy is when asshats make it personal. Disprove everything I say -- that's part of the fun -- but do it with a civil tongue.

 

[Jay Honeck]

Of course you would abort. You would have eventually stalled if you continued to hold a 45 degree attitude. Not sure the point of your original 45 degree statement. A mighty Cherokeee 140 can hold 45 degrees for an amount of time as well.

Why would anyone hold a specific deck angle? When holding Vx -- you fly a specific speed, not a specific deck angle.

For the third (?) time, in the -8, the deck angle after stabilization at Vx was excessive -- so we aborted and dropped the nose to Vy.

 

[Jay Honeck]

Its is very useful to know how much runway you need to stop (based upon your current speed.) There is a point on the runway that you cannot safely land any longer, and would overrun. As speed increases the distance required increases. So that can be an issue if you are doing 120-140mph in a slick aircraft with 1000ft remaining of runway.

Very good point. Unfortunately, I can't think of a way to test this parameter without compromising safety.

What I need is an old Space Shuttle landing field, where I could test an aborted departure to landing.

 

[Jay Honeck]

Complete and utter horse hockey. I've owned an RV. I've flown most of the models, including the RV8. I've climbed at Vx. I've flown all the Pitts models. I've climbed those at Vx. You seem to think the RV is a 350 hp MX. It's not a great idea in these ultra high performance airplanes to climb at Vx ASAP immediately after breaking ground due to the very high deck angle, which may box you into in situation from which you cannot recover if your engine quits on low climbout. That is accepted among pilots of these types of ships. The RV is simply not nearly as extreme as you think. I know lots of RV pilots. I've got hundreds of hours in an RV4. The RV8 handles like a boat in comparison. I've never heard of this "nobody in their right mind would climb at Vx" bullsh!t. But maybe I need to read more "articles" rather than actually flying.

Well, I guess there are a lot of idiots flying -8s who don't feel comfortable departing an airport with zero forward visibility and compromised cooling. Count me as one of them.

 

[Jay Honeck]

So the suggestion made earlier to Jay to determine V1 has no bearing to this discussion?

Very few of the suggestions made in this thread have had any bearing on the discussion.

 

[MAKG1]

Very good point. Unfortunately, I can't think of a way to test this parameter without compromising safety.

What I need is an old Space Shuttle landing field, where I could test an aborted departure to landing.

Will a dead SAC base do? Those are 12000 foot runways. You don't need the KEDW 7 mile monster for this.

Some large Class C airports have runways that long, too. KAUS comes to mind.

 

[flyingmoose]

Wayne, I guess I am just to dumb to get what you are talking about. I am just trying to figure out how a non existent number (V1) for this aircraft relates to this thread. I certainly agree that in your scenario you will not get it stopped. In fact I agree with the general consensus regarding the fallacy of Jay's original assumption. I just don't understand the V1 tie in.

You are not dumb, it really doesn't have any relevance to this thread. You could figure out what that number is, but it is always changing and is different for every runway that you take off on. Its mostly dependent on runway and not a hard number to remember. If you want to come up with an accelerate stop distance, you can, but most runways that rv-8 type a/c operate on have plenty of distance remaining. If you have an engine failure in a single after or before that speed it makes no difference, you are going to land somewhere, so it doesn't matter.