Max performance climb, high G, split Ess

[Jaybird180]

The Blue Angels opposing solo does this maneuver with full fuel from a standing takeoff.

If I replicate this maneuver (hypothetically of course) in something like an Ercoupe (or something suitable, with moderate power In the normal category - no disrespect toward Ercoupe fliers) what would be required?

So, we roll down the runway until reaching flying speed, then remain in ground effect at max power. If we give a hard pull at exactly Va while still accelerating, at what G force will this be? What is the effect on stall performance? How can we calculate the altitude gain before the stall is imminent?

 

[poadeleted20]

If I replicate this maneuver (hypothetically of course) in something like an Ercoupe (or something suitable, with moderate power In the normal category - no disrespect toward Ercoupe fliers) what would be required?

A lot more power than an Ercoupe has.

So, we roll down the runway until reaching flying speed, then remain in ground effect at max power. If we give a hard pull at exactly Va while still accelerating, at what G force will this be?

Well, at Va, the airplane will stall before it reaches limit g, and limit g on that plane is about 4 g's. However, as soon as you pull like that, airspeed will start to drop, and you won't be able to maintain the g-force without stalling. In addition, gravity will be working against you, further decelerating the plane. As a result, you'd have to enter the pull with a lot more speed than Va. All in all, with the power available, I'm not sure you can get an Ercoupe going fast enough to do a high-g half-Cuban-8 like Blue 6 does.

What is the effect on stall performance?

It doesn't change stall performance -- the aircraft will stall when the critical angle of attack is exceeded. If you're asking about the speed at which it will stall in a wings-level pull, the answer depends on how much g you're pulling.

How can we calculate the altitude gain before the stall is imminent?

It will depend on entry speed and g-force in the pull, but in an 'Coupe, I doubt you'll get much past 45 nose-up no matter what you do, and probably somewhere around 500 feet of altitude gain -- think of the last time you did a power-on stall.

 

[Jaybird180]

It doesn't change stall performance -- the aircraft will stall when the critical angle of attack is exceeded. If you're asking about the speed at which it will stall in a wings-level pull, the answer depends on how much g you're pulling.

Please forgive the example plane but I was describing, or attempted to describe a zoom. Surely some normal category plane can do this???

 

[poadeleted20]

Surely some normal category plane can do this???

No doubt, but it would have to have a pretty good power/weight ratio, and of course, it wouldn't be legal in a Normal category aircraft even if it was capable of doing it. Biggest problem would be reaching entry speed before disappearing out of sight -- that's where a couple of F404 engines in max AB really help. Without a enough speed at the start (or a thrust:weight ratio better than 1:1), you'll run out of speed or stall before you get enough altitude to roll over and complete the half-Cuban-8 without hitting the ground on the back side.

Obviously, if you just put the nose up into a Vx climb, you can just climb up at a relatively steep angle until you have enough altitude for the second half of the maneuver. Only problem is that's not all that exciting a manevuer to watch. But if you run for a lot of speed and then pull really hard in a light plane with insufficient thrust:weight (e.g., anything that isn't an Extra 300 or a Sukhoi 26 or a Yak 54 or the like), you're going to run out of energy before you have enough space below you to roll over and pull though back to level flight the other way.

 

[kgruber]

The Blue Angels opposing solo does this maneuver with full fuel from a standing takeoff.

If I replicate this maneuver (hypothetically of course) in something like an Ercoupe (or something suitable, with moderate power In the normal category - no disrespect toward Ercoupe fliers) what would be required?

Another 400 horsepower.

 

[Capt. Geoffrey Thorpe]

Please forgive the example plane but I was describing, or attempted to describe a zoom. Surely some normal category plane can do this???

To "zoom" you are trading off airspeed for altitude - so you want something that can build a lot of speed quickly. Then you get to zoom up a bit as the air speed bleeds off. At some point you have to push the nose back down for a normal climb. The G loading would depend on how hard you pull to transition from level flight to the zoom.

Something like an Ercoupe where you can pick up an extra 10 mph or so you can zoom dozens of feet. :wink2:

 

[Jay Honeck]

If I replicate this maneuver (hypothetically of course) in something like an Ercoupe (or something suitable, with moderate power In the normal category - no disrespect toward Ercoupe fliers) what would be required?

JATO.

 

[Richard]

Jay blew it by mentioning the Ercoupe. He attempted to correct that by mentioning "any normal category" aircraft. That hardly made a diffenerence since it seems the main topic here is thrust:weight ratio. Therefore, it is confusing to mention any aircraft type. However, I think his purpose was to propose an aircraft most of us have access to.

There just isn't a substitute for horsepower. Even Tim "Tool time" Allen knew that.

I propose one should try this at above a 'hard deck' of 3,000 agl. Enter the pullup in a dive. A Decath could do it. It can't be a hard pull...that's like cavitating a rudder by turning hard over...it exceeds AoA.

 

[Steve]

JATO.

http://vimeo.com/875011

 

[AcroBoy]

I think the OP is describing an Immelmann (half loop then half roll), and not a split S (half roll then half loop down) at least I hope. It is possible to do a half loop from as slow as 80k in a Super Decathlon, but it takes some finesse. In an Extra loop entry speed is generally around 160k, but of course can be lower or higher.

So, yes it's possible, and shouldn't need a diving entry.

 

[PittsDriver]

I'm not sure what maneuver you're talking about. If one where you start your roll, take off and stay in ground effect, and pull up through a half loop or half cuban (5/8ths of a loop) then there are lots of single engine airplanes that have the performance for that maneuver - setting aside for the moment if it's legal or not. For my Pitts, it's no problem and I've done something similar in an RV-7 and it also had plenty of margin.

If you're talking about the reverse of this - which is to say that you take off and climb out at, say, Vx until you get to a safe altitude where you then roll inverted and pull down through a reverse half-cuban to a level pass down the runway. Also not a problem but in an airplane with weak climb performance it might take a while and be out of sight before you can attempt the down loop. The risk in this one is misjudging the altitude you need before you pull at the ground. Once you get close to vertical through the loop down you're committed to whatever altitude loss you're going to get - whether it puts you in the dirt or not. The reverse half cuban is considered by many to be one of the most dangerous air show/surface level acro maneuvers to fly because you're pulling your energy toward the ground at low altitude. More than a few pilots have been ended by misjudging the altitude gate for this.

And of course, none of it would be legal without being in waivered airspace with a ACE card down to the floor of the maneuver you're flying regardless of what airplane you're flying.

 

[Fearless Tower]

http://vimeo.com/875011

That photo is just F'n AWESOME!

 

[nosehair]

Ess? You called it an "Ess"? A Split-Ess?

I've never seen it described with the letter "S" spelled out.
(you do know it is a letter 'S', right?)
(split? -in half, ..the lower half)

 

[GeorgeC]

At least he didn't call it a split-p.

 

[Henning]

Please forgive the example plane but I was describing, or attempted to describe a zoom. Surely some normal category plane can do this???

A zoom climb is not what the title describes.... Yes, any plane can do a zoom climb. If you are in smooth air you do not restrict yourself to Va, there is no need and you will not have any energy to "zoom" with. If you want to do a "Zoom" climb in the Ercoupe is simple. Take off and level out just above the runway until you hit your max speed. Now pull a smooth 3Gs so you're peaking Gs at a 45* deck angle. For low power aircraft, 3Gs is a very effective balance between transition speed and the energy lost, so now you're on the vertical. There are Two ways you can play out of the vertical, you can ease you're way out in a nice ballistic style trajectory, or you can play out all your excess speed in the vertical or near vertical line and then push over to catch the airplane at Minimum Controllable Airspeed and then accelerate again in level flight. You can also add a rotation to the last maneuver and come out on downwind for a "tight" pattern.

 

[Richard]

At least he didn't call it a split-p.