Departures: Vx, Vy, or Zoom

[frfly172]

Wow a lot of hostility in these posts.as for v1 we used that in jets and turbo props.I thought single engine pistons where more concerned with density altitude and distance to clear a 50 ft obstacle.jay enjoy the fact that you made a lot of people happy by opening this thread.enjoy your rv and fly it how you are comfortable.

 

[RoscoeT]

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.

Cooling issues?? Are you serious? Maybe we should review the purpose of Vx - to clear obstacles and gain the max altitude for a given forward travel. Climbing at Vx beyond pattern altitude is totally pointless. So you think you're going to cook your cylinders climbing no more than 1000' AGL at Vx?? Is your fancy RV not equipped with CHT and oil temperature so that your can monitor all these "cooling issues" you think you might have climbing at Vx for 30 seconds or so?? That being said, there is rarely truly a need to climb at Vx in an RV.

And as far as forward visibility goes - can you see under the nose at Vy? Nope. So why are you so worried about seeing under the nose at Vx? You know what those rudder thingies are sometimes good for? Moving the nose out of the way for a second so you can see what's in front of you. Ever fly a Pitts or anything with a radial engine? You really don't know what forward vis issues are in an RV. Not a problem in these visiblity challenged airplanes either. Forward visibility is overrated by those who have only flown tricycle trainer types.

 

[X3 Skier]

No idea why no over the nose visibility at Vx is a problem since flying at Vx is to clear an obstacle which is in the way and once I am at the altitude to clear it, I can use Vy. Since I know the location of the obstacle(s) and it's height from preflight planning, the fact that I can't see it over the nose is irrelevant.

if my preflight planning doesn't show I can clear it that day at the required Vx because of density altitude or gross weight or phase of the moon, wait till I can. If it would make me nervous or if I have to wait till winter, I suppose I shouldn't have flown to that airport in the first place.

Cheers

 

[ronnieh]

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.

Well actually Bruce and Wayne make good points. First, Wayne was simply trying to get me to understand the COMPLETE definition of V1. Bruce was pointing out if one is going to fly a plane a couple of feet above the runway you might want to know at what point you will not have enough runway to stop. Both are good points. I was just focusing on the multi engine aspect of V1 which of course does not relate. The concept of balance field does.

 

[Sam D]

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 -- was your deck angle on your zoom climb less than the Vx climb?

 

[ronnieh]

Wow a lot of hostility in these posts.as for v1 we used that in jets and turbo props.I thought single engine pistons where more concerned with density altitude and distance to clear a 50 ft obstacle.jay enjoy the fact that you made a lot of people happy by opening this thread.enjoy your rv and fly it how you are comfortable.

Generally the concept of V1 is for turbojets and other multi engine aircraft over 12,500 pounds. V1, Vr and V2 would have to be calculated for each departure. I do not think this information exists for aircraft other than those I mentioned. It does seem like I have heard that accelerate/stop distances are published for some piston twins. I suspect if this is true the charts pick out a couple typical conditions but, do not give actual information to calculate this number for all situations. Sorry for the extreme thread drift I caused.

 

[lr60plt]

Unless you are an experienced aerobatic pilot or you have a sight gauge, you probably have no idea what 45 degree looks like in that plane, as there was no way you were even close to it. Id bet it was something more like 25-30 degrees max.

 

[Skylane81E]

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.

Can you say brake fire?

 

[rwellner98]

Unless you are an experienced aerobatic pilot or you have a sight gauge, you probably have no idea what 45 degree looks like in that plane, as there was no way you were even close to it. Id bet it was something more like 25-30 degrees max.

Maybe he has an attitude indicator.

 

[flibmeister]

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.

Yeah, couldn't agree more. But, unfortunately we have people on here who think it appropriate to do things like starting a thread FOR THE EXPRESS AND ONLY PURPOSE of showing disrespect for a bunch of people he never met (every pink-shirted Oshkosh controller, expanded to include every non-military federal employee)-- based on nothing more than his distaste for the actions of their employer. Who does that? Talk about asshats!

Oh, wait.... that was you. Karma's a *****, Jay.

 

[lr60plt]

Maybe he has an attitude indicator.

What degree does your attitude indicator go up to? Most stop at 20 maybe 30 degrees. Id be very surprised if his went anywhere near 45 and can guarantee that's not what he was looking at when he thought he was doing it.

 

[wabower]

He said the indicator used for this maneuver was his wife.

Maybe he has an attitude indicator.

 

[JoeSelch]

I climbed out at 70-75 kts twice today in my RV-6.
I'm not certain, but I'm guessing it must be woefully underpowered compared to the almighty "HP" RV-8A, as it was a total yawn both times.

 

[somorris]

I think Jay just proved Vy is better than a zoom climb. I usually use Vy to provide better engine cooling (I have to pay for repairs). I like to do whatever I can to reduce maintenance costs. I fly (most of the time) off a 6,000' runway and have had to land and stop before. Vy allows that with acceptable safety margins for me. Everybody has to pay their money and make their choice .

 

[redtail]

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.

As well as Class D, Stewart Intl (KSWF) in Newburgh, NY comes to mind. 11800'

I'll never forget my first landing there as a student. It felt odd landing a skyhawk on such a long runway!

 

[wabower]

What amount of additional heating do you notice in climbing to traffic pattern altitude at Vx rather than Vy? Is the time required more or less than two minutes?

I think Jay just proved Vy is better than a zoom climb. I usually use Vy to provide better engine cooling (I have to pay for repairs). I like to do whatever I can to reduce maintenance costs. I fly (most of the time) off a 6,000' runway and have had to land and stop before. Vy allows that with acceptable safety margins for me. Everybody has to pay their money and make their choice .

 

[MAKG1]

What amount of additional heating do you notice in climbing to traffic pattern altitude at Vx rather than Vy? Is the time required more or less than two minutes?

Vy is the maximum rate of climb, and will always result in less time to a given altitude than Vx.

I've never flown an RV, but I find most of the aircraft I fly aside from the 172s/PA28s start to get pretty hot after about half a minute of Vx climbing at full throttle and max RPM. There is a reason the checklists say to pitch down to Vy (or sometimes even slower) when the "obstacles have been cleared."

 

[wabower]

Which planes other than the Skyhawks and Cherokees that you fly have demonstrated this problem? Which temps are you measuring? Does this 30 second-period include the time from brake release, or do you hack the temp at rotation?

Vy is the maximum rate of climb, and will always result in less time to a given altitude than Vx.

I've never flown an RV, but I find most of the aircraft I fly aside from the 172s/PA28s start to get pretty hot after about half a minute of Vx climbing at full throttle and max RPM. There is a reason the checklists say to pitch down to Vy (or sometimes even slower) when the "obstacles have been cleared."

 

[denverpilot]

I stopped reading last night at two "experienced" pilots missing that Vy was a lower speed than Vx. And then didn't bother posting this until today because I got busy. LOL.

 

[Jay Honeck]

Jay -- was your deck angle on your zoom climb less than the Vx climb?

A steep deck angle at 75 knots is much different than a steep deck angle at 140 knots. At 75 knots, if the big fan stops you are indeed in deep doo doo, and have very little time to get the nose down before a stall.

To illustrate further, I am comfortable going straight up in the -8, so long as I have airspeed.

 

[Jay Honeck]

Unless you are an experienced aerobatic pilot or you have a sight gauge, you probably have no idea what 45 degree looks like in that plane, as there was no way you were even close to it. Id bet it was something more like 25-30 degrees max.

Correct. Lacking instrumentation, I have no idea what the actual deck angle was. I am going by my wife's estimate, with her seated beneath and behind me in the back cockpit.

It could have been 30. It could have been 50. For purposes of discussion, the precise deck angle is not important.

 

[Jay Honeck]

Yeah, couldn't agree more. But, unfortunately we have people on here who think it appropriate to do things like starting a thread FOR THE EXPRESS AND ONLY PURPOSE of showing disrespect for a bunch of people he never met (every pink-shirted Oshkosh controller, expanded to include every non-military federal employee)-- based on nothing more than his distaste for the actions of their employer. Who does that? Talk about asshats!

Oh, wait.... that was you. Karma's a *****, Jay.

Take it to the Spin Zone. I don't discuss politics here.

 

[wabower]

You didn't seem to have any problem with it during your earlier rant. Why now?

Take it to the Spin Zone. I don't discuss politics here.

 

[Jay Honeck]

I had a long discussion with our transition trainer about these departure options last night. Tom is a man with thousands of hours in RVs, makes his living entirely within the RV world, and is regarded as a leader in the homebuilt world.

His preferred departure procedure (and it's the one he taught us) is quite simple, and has no connection to V speeds at all: Put the glareshield on the horizon.

This allows for maximum forward visibility, with better than Vy cooling. In his opinion (and I concur) THIS is truly the "safest" departure method.

WRT a Vx departure, he agrees that the -8's extreme deck angle at relatively low airspeed compromises cooling, reduces forward visibility to zero, and is only needed on that rare occasion when you're on an extremely short strip with big obstacles at the end of the runway. If the big fan quits during this type of departure, the pushover to prevent a stall will be extreme.

WRT zoom climbs, he just chuckled and said "They're a lot of fun."

 

[RoscoeT]

At 75 knots, if the big fan stops you are indeed in deep doo doo, and have very little time to get the nose down before a stall.

No - pushing the nose over is NOT about stall avoidance, it's about airspeed maintenance. Every student pilot learns that a stall is a function of AOA, not airspeed. Go up in your RV and pull the throttle to idle while climbing at Vx. Do nothing with the stick, just hold it and wait. You will not stall. You will simply fly a tight parabolic arc with very little airspeed over the top before the nose ends up below the horizon with airspeed building. You'll only stall if you pull the dang stick into your gut. In a true engine-out situation, you simply need to be careful to avoid attempting to raise the nose from the nose-down position too quickly or agressively. But this oft-repeated stuff about "nose down or else you'll stall" is just wrong from an aerodynamic standpoint.

 

[Jay Honeck]

No - pushing the nose over is NOT about stall avoidance, it's about airspeed maintenance. Every student pilot learns that a stall is a function of AOA, not airspeed. Go up in your RV and pull the throttle to idle while climbing at Vx. Do nothing with the stick, just hold it and wait. You will not stall. You will simply fly a tight parabolic arc with very little airspeed over the top before the nose ends up below the horizon with airspeed building. You'll only stall if you pull the dang stick into your gut. In a true engine-out situation, you simply need to be careful to avoid attempting to raise the nose from the nose-down position too quickly or agressively. But this oft-repeated stuff about "nose down or else you'll stall" is just wrong from an aerodynamic standpoint.

So, to recap, you're saying that if the engine quits at 15' AGL, in a 30 degree (or whatever) up angle, at Vx, that I can hold the stick precisely in the same position and not stall?

Okay, let's say that's true -- your "tight parabolic arc" into the ground sounds just as perilous. The end result is you either do an incredibly abrupt pushover pretty much instantly, or you scatter parts down the runway.

Methinks I will just avoid doing Vx departure unless they are absolutely necessary.

 

[RoscoeT]

So, to recap, you're saying that if the engine quits at 15' AGL, in a 30 degree (or whatever) up angle, at Vx, that I can hold the stick precisely in the same position and not stall?

I don't know how it's even up for discussion. Yes. It's physics. That does not mean you will not hit the ground in a regretful way. But it will not be because the airplane stalled. I still haven't found a way to exceed critical AOA in any airplane while holding the stick around neutral.

Okay, let's say that's true -- your "tight parabolic arc" into the ground sounds just as perilous. The end result is you either do an incredibly abrupt pushover pretty much instantly, or you scatter parts down the runway.

Let's say that's fact. Yes, a low-altitude engine failure does take action on the part of the pilot. My point is let's not throw around false aerodynamic statements.

Methinks I will just avoid doing Vx departure unless they are absolutely necessary.

Fine, they are very unnecessary in an RV. RVs will always need more distance to get in than get out. If you got in, getting out will never be in question - even at Vy.

 

[Jay Honeck]

I don't know how it's even up for discussion. Yes. It's physics.

Well, thanks for that. This is why I come here -- to learn.

I think most pilots misuse the scientific term "stall", and apply it to many low altitude situations where "mush", or "tight parabolic arc" is more accurate.

The end results are the same.

Luckily, the method required to avoid all three conditions is the same. Airspeed is your friend.

 

[Henning]

Well, thanks for that. This is why I come here -- to learn.

I think most pilots misuse the scientific term "stall", and apply it to many low altitude situations where "mush", or "tight parabolic arc" is more accurate.

The end results are the same.

Luckily, the method required to avoid all three conditions is the same. Airspeed is your friend.

Not when you're crashing it's not. When the engine ****s the kitty in a SE plane on take off, I want to be going as slow as possible with as much runway in front of me as possible. The Vx climb is as much your friend as anything else, the key is to fly the freakin airplane to the edges of the envelope with full confidence and control.

 

[denverpilot]

Methinks I will just avoid doing Vx departure unless they are absolutely necessary.

Vx at our DA is sometimes really needed because climb rate is so adversely affected by hot and high operations.

I do a Vx departure once in a while just to know how mushy the aircraft feels and how damn high that glare shield really sits. If you don't go do them once in a while, you'll have a tendency to relax back pressure on a day you really need it.

Ironically you may need it on a day with an incredibly long runway. A departure from KLXV on a really hot day for example, you may need it to clear the trees on the north end. Other than the cowl blocking everything, the Vx speed will give what appears to be a shallow Vy angle of climb all the way to the trees. Vy might put you into the trees. Or force you to fly through the gap to the left side in the tree line.

There's a reason the Colorado Pilots Assn requires everyone flying their training flights to put a hard stop on departing KLXV above 75F at the surface. I've done that takeoff with two aboard and half tanks and used Vx and every available inch of runway, and cleared those trees by roughly 100' AGL in the Skylane.

Because it was done in controlled and double-checked conditions with a CFI, the outcome was not in any doubt and matched book numbers even though we were off the chart and needed to extrapolate. The brain opener was that the eyeballs are quite unhappy with the view out the front window because it seems like it's too weak a climb and the angles and distances look wrong. You fight a strong desire to pull the nose further up slower than Vx as the trees get bigger.

Then the CFI casually points out the hole in the tree line to your left was your "out" as you pass it out your pilot's side window, and you never forget it... You also gain a first hand appreciation of the book numbers for climb out distances for "50' obstacles". And realize the trees are higher than 50'. And you cleared them with 100' feet to spare. And how much your butt puckered. And how pushing those book numbers is something you might always want to have at least a significant margin for airspeed error and piloting technique.

Highly recommended. Being the RV up and do the course sometime. You'll have fun and it's a beautiful view.

 

[Skylane81E]

My first take off from LXV AWOS reported
"Density altitude one three thousand"

VX and flaps 10 with one passenger and 1/2 tanks still used most of the runway.

 

[Bill Watson]

A steep deck angle at 75 knots is much different than a steep deck angle at 140 knots. At 75 knots, if the big fan stops you are indeed in deep doo doo, and have very little time to get the nose down before a stall.

To illustrate further, I am comfortable going straight up in the -8, so long as I have airspeed.

see below...

No - pushing the nose over is NOT about stall avoidance, it's about airspeed maintenance. Every student pilot learns that a stall is a function of AOA, not airspeed. Go up in your RV and pull the throttle to idle while climbing at Vx. Do nothing with the stick, just hold it and wait. You will not stall. You will simply fly a tight parabolic arc with very little airspeed over the top before the nose ends up below the horizon with airspeed building. You'll only stall if you pull the dang stick into your gut. In a true engine-out situation, you simply need to be careful to avoid attempting to raise the nose from the nose-down position too quickly or agressively. But this oft-repeated stuff about "nose down or else you'll stall" is just wrong from an aerodynamic standpoint.

Absolutely correct is theory and in practice. If you actually do a Vx engine out transition to a glide, letting the nose fall without pulling or pushing too much is the way it works. If you are mentally preloaded to push it over you will overdo it. Try it, you'll see.

I had a long discussion with our transition trainer about these departure options last night. Tom is a man with thousands of hours in RVs, makes his living entirely within the RV world, and is regarded as a leader in the homebuilt world.

His preferred departure procedure (and it's the one he taught us) is quite simple, and has no connection to V speeds at all: Put the glareshield on the horizon.

This allows for maximum forward visibility, with better than Vy cooling. In his opinion (and I concur) THIS is truly the "safest" departure method.

WRT a Vx departure, he agrees that the -8's extreme deck angle at relatively low airspeed compromises cooling, reduces forward visibility to zero, and is only needed on that rare occasion when you're on an extremely short strip with big obstacles at the end of the runway. If the big fan quits during this type of departure, the pushover to prevent a stall will be extreme.

WRT zoom climbs, he just chuckled and said "They're a lot of fun."

Yep, that's what just about everyone does. Proficiency means that you can handle them all from Vx to Zoom climb, and knowing when or why to do which one.

Well, thanks for that. This is why I come here -- to learn.

I think most pilots misuse the scientific term "stall", and apply it to many low altitude situations where "mush", or "tight parabolic arc" is more accurate.

The end results are the same.

Luckily, the method required to avoid all three conditions is the same. Airspeed is your friend.

Please stop the insanity Jay. Sarcasm has it's place but not when your pants are down.

Airspeed being your friend is a good thing to hang on to but it's not enough if you are going to be pulling your '8 around the sky. The guy who talks about'+1G' zoom climbs is going to be a bit confused when confronted with an accelerated stall at 140knots. Ever done an accelerated stall? Get your RV transition guy or someone comfortable doing acro in an RV to show you one. Expand your mind. Please.

Oh, and let me know what it's like. I've done them in trainers but I'm too chicken to play around with them in an RV. Certainly not my '10.

 

[kyleb]

Oh, and let me know what it's like. I've done them in trainers but I'm too chicken to play around with them in an RV. Certainly not my '10.

Accelerated stalls in the short wing RV's are non-events, as long as the airplane is correctly rigged and the ball is in the center.

Set up for straight and level 75 knot flight, then bank to 45 degrees and pull until it stalls. Should be a non-event...

Do it at altitude, just in case.

 

[Bill Watson]

Accelerated stalls in the short wing RV's are non-events, as long as the airplane is correctly rigged and the ball is in the center.

Set up for straight and level 75 knot flight, then bank to 45 degrees and pull until it stalls. Should be a non-event...

Do it at altitude, just in case.

Agreed, that should be a non-event. Some time ago I did some 'more aggressive' types and I guess I just worked it out of me.

Had a CFI demonstrate some 'secondary' stalls, that is stalling it after a stall recovery with the nose pointed well down. I think that qualifies as a kind of accelerated stall. That was a pretty good lesson.

The CFI who like to do snap rolls in a C172 on the way back from the practice area, not such a good lesson.

 

[MSPAviator]

I fly mostly for fun, so I'll pick the Zoom Climb because it's the most fun. I normally don't do the zoom climb unless I am under gross though.

 

[MAKG1]

Which planes other than the Skyhawks and Cherokees that you fly have demonstrated this problem? Which temps are you measuring? Does this 30 second-period include the time from brake release, or do you hack the temp at rotation?

I've seen it in Skylanes, Cardinals (RG), and Cutlasses. It's the CHT that makes me sweat, as full-open cowl flaps aren't enough.

 

[Jay Honeck]

Had a CFI demonstrate some 'secondary' stalls, that is stalling it after a stall recovery with the nose pointed well down. I think that qualifies as a kind of accelerated stall. That was a pretty good lesson.

We did lots of secondary stalls in the -8. So long as the ball is centered, any type of stall in the -8 is a non-event.

I am looking forward to spin training in it.

 

[Jay Honeck]

Please stop the insanity Jay. Sarcasm has it's place but not when your pants are down.

Airspeed being your friend is a good thing to hang on to but it's not enough if you are going to be pulling your '8 around the sky. The guy who talks about'+1G' zoom climbs is going to be a bit confused when confronted with an accelerated stall at 140knots. Ever done an accelerated stall? Get your RV transition guy or someone comfortable doing acro in an RV to show you one. Expand your mind. Please.

I'm not following you. Where was I being "sarcastic"?

Sorry if my terminology doesn't suit your needs. I thought calling it a "+1 G pull" was pretty obvious, but apparently not. If you would rather that I call it a "2G pull", because your body is feeling the effects of 2Gs, rather than a "PLUS ONE GEE" pull, well, I can adjust in the future.

Finally, your assumption that I haven't done stalls of every kind in the -8 is, as with most of the assumptions in this (and other) threads, wrong.

 

[Bill Watson]

I'm not following you. Where was I being "sarcastic"?

Right here:

Well, thanks for that. This is why I come here -- to learn.

I think most pilots misuse the scientific term "stall", and apply it to many low altitude situations where "mush", or "tight parabolic arc" is more accurate.

The end results are the same.

Com'on, let's not play games.

Again, I think you are a level headed responsible type pilot. The transition training was smart, your instructor sounds totally competent. I'm sure you did the usual stall sequences.

My point about stalls revolves around your thing about 'airspeed is your friend'. It's a good truism but it's not a good response to someone talking about angle of attack is what stalls are about. So you did some secondary stalls - did you look at your airspeed indicator when you did them? CFIs, correct me, but the point of secondary stall training is to demonstrate that you can stall at higher than 'stall speed' airspeeds. You pull back on the stick abruptly enough at any airspeed and you will stall... or pull the wings off.

 

[Jay Honeck]

Right here:

I'm still not getting it. You think I don't come here to learn?

You're wrong...AGAIN.

The only reason to hang out in these groups is to learn about aviation. When that ceases to occur, you will cease to see me.

I don't see myself running out of new tidbits any time soon, though, so don't get your hopes up.