Spycams and Hammerheads

I bought a MD80 "Spycam" on eBay for $12 and mounted it on my RV8's wing tip. I made a small aluminum mount and screwed it in to the existing plate nuts. Here's a short movie I made a couple of months ago: http://www.youtube.com/watch?v=06tyP-Jj834.

The camera has enough battery to last about 1 hour. The micro SD Card I have is good for about 25 minutes of video. Since I have to start recording before starting the plane, there is barely enough time to get out to the practice area.

The hammerheads at the end of the video are not as vertical as I intended for them to be. They seemed fine when I was doing them.

On the subject of hammerheads, I have been doing them in my RV8 for about a year. I do them because there is a hammerhead in the IAC Sportsman sequence and because they are really a lot of fun.

I have never had a problem with hammerheads until a month ago. I did one where I unintentionally waited too long before starting the pivot. I think I was also pitched beyond vertical. When pressed down on the rudder pedal there was no resistance and the plane didn't respond. It stayed more or less vertical at full power and full left rudder for what seemed to be a couple of seconds. It then fell over on its back and started to rotate at the same time. As the nose passed through the horizon I chopped power and centered the controls and rudder. Slightly opposite rudder as the nose dropped down immediately stopped the rotation. I eased back on the stick to go vertical down and then pulled to level off.

I love doing hammerheads. Still, I will only do them wearing a parachute, at fwd CG (i.e. solo in my RV8) and with lots of recent spin practice.

I know that feeling about the rudder... It feels like the cable has become disconnected, right? Very disconcerting... I got that same feeling on the elevator, but I was doing a hamerhead too. I also left it a tiny bit too long before the pivot and fell out, but it fell forward onto it's belly. I pushed the nose down, then tried too soon to pull back and recover, and that same "disconnected" feeling came with the stick all the way to my lap. Had to center the stick again and wait for it to speed up a bit to get enough control authority to try again. Ah well. That's why we do these things at 4-5000' AGL when we're learning, right?

nice video

Luis,
Nice video and write up with the hammerhead adventure. I especially noticed your beautiful RV-8 and went to your website for pictures and found your write-up on your first IAC contest: http://www.flugeron.com/fun/08312008.htm That's exactly the impression I had too, and hope other RVers will come join the fun.
Thanks,
Bill McLean
RV-4 Slider

Thanks Bill.

Does anyone know of a good technique for picking the right time to start the pivot? I have been using my airspeed indicator (30kts) but this is hard to do while looking at the wing tip. I have also tried yarn on the wing tip with no success. It doesn't seem to do anything different on the way down to 30kts.

Hmm

30kts works good on the 7.

If you had held the control inputs ypu might have done an inverted spin..As me how I know...

Frank

No experience in power planes. In the glider I look at the wing tip and start the pivot when the wind noise sounds about right. I never look at the ASI for that. Once I started the pivot, I keep my eyes at the horizon to check how much opposite aileron I need to keep the plane from rolling on its back (long wing span -> upper wing produces much more lift). When I'm almost through the turn I look straight down and check if I need to cheat and change the direction by a bit of roll during the vertical.

In a glider starting the pivot too early has a very similar effect to starting it too late. If I start too late, I'm too slow to make it all the way round, and the plane starts falling down sidewards until the nose drops down. If I start too early, the plane side-slips upwards, the tail acts as a vane preventing the plane from turning, I lose lots of energy until the plane is too slow and starts falling down sidewards.

If there is any danger of sliding backwards, don't let the controls go. You don't want them being banged into the stops by the reversed air flow.

FrankH 30 Knots is too slow for my 7A

lluciani, if your add right rudder as the nose passes the horizion in the kick, you'll avoid the nose reacting like a pendelum on the down line.

Nice video

Stripes

lluciani
I am reluctant to post an opinion as I am no expert when it comes to aerobatics.
However, here goes.
You appear to be describing a late rudder application with possibly an incipient Tail Slide.
A Tail Slide is a potentially dangerous as it can produce structural damage to control surfaces, especially if not handled correctly. Very bad to have elevator, or rudder, or aileron deflected even a little whilst airflow reversed. Must centralise all conrols and hold them rigidly centralised until aircraft is out of Tail Slide. I suggest you read further on this in any of the good aerobatics books, or speak to a qualified aerobatics instructor.
Secondly, as FrankH said, not hard to get into an inverted spin if a stall turn goes wrong. On upline, especially if over do the inittial pich line and tryintg to correct, if slow at top with slightly forward stick, as you "kick" rudder at top , have perfect set up fpr inverted spin (below stall, wing dropping, forward stick). It can happen fast and be VERY disorienting as unexpected and inverted spin is odd feeling and visually.
Again I suggest you speak to a qualified aerobatics instructor about both how to handle an inadvertent Tail Slide, and inverted spinning.
Best wishes
John

Inverted spin! Oh my!

Luis,

Don't let the "experts" get you down. If someone on this forum has ever experienced an inverted spin in a RV, please chime in here. And if someone has by some stroke of luck, skill or genious entered an inverted spin and was unable to get out of it by simultaneously scratching their behind and picking their schnozola, please let us know.

I have spent hours trying to get my RV to spin better and the "experts" keep telling me that I might accidently succeed. I wish!

Ron
As I said I don't claim to be an expert.
Definitely not trying to frighten anyone - aero's are fun and any pilot can do them safely if trained/knowledgeable, but there are some traps.
RV's aren't unique in aerodynamic terms.

However you are correct in one thing - most aircraft inehently want to come out of an inverted spin so recovery by Beggs method is easy.

John

I have

Categorically done an inverted spin on the 7a..It snapped into it fast. Now it would NOT do it solo..I tried hard many times to make it spin inverted.

Then one day I had a fairly heavy PX and over rotated a little on the upline..Had full forward stick and kicked the rudder.

It span inverted very nicely...It also recovered very well.

I have not had the courage to re-create the event, even though Steve Wolf ran me through a number of them in his Zlin trainer.

I keep telling myself I'm going to go film it one day..

Frank

ronschreck said:

Luis,

Don't let the "experts" get you down. If someone on this forum has ever experienced an inverted spin in a RV, please chime in here. And if someone has by some stroke of luck, skill or genious entered an inverted spin and was unable to get out of it by simultaneously scratching their behind and picking their schnozola, please let us know.

I have spent hours trying to get my RV to spin better and the "experts" keep telling me that I might accidently succeed. I wish!

Click to expand...

Glad to see Bill Finagin made you a believer Ron.....Best training ever huhh? he is coming back to KLKR after Sun and Fun! Let's get some of the other RV team guys trained!

lluciani said:

Does anyone know of a good technique for picking the right time to start the pivot? I have been using my airspeed indicator (30kts) but this is hard to do while looking at the wing tip. I have also tried yarn on the wing tip with no success. It doesn't seem to do anything different on the way down to 30kts.

Click to expand...

ASI is not a very good way since most don't read low enough, as well as the fact that your eyeballs are inside the airplane, and not on the wingtip maintaining your vertical line.

The most common method acro pilots use to judge the timing of the pivot is with aileron. Does your airplane start to torque-roll at all as it gets very slow at the top? Do you need right aileron to prevent this? In the Pitts, when right aileron reaches a certain point as it's being fed in to control the torque roll, it's time to pivot. This is a good consistent indicator. If your plane doesn't actually torque roll, you could probably gauge the timing by feeling for the point when the ailerons are deadening, start feeding in right aileron, and when you get to a certain deflection with no roll reaction (progressive input), you can start your pivot.

Can you feel a tell-tale buffeting of the airframe as you reach the top? Some airplanes display this, some don't. The tightening slipstream at high power and very low airspeed can cause a specific buffeting that some use to gauge the timing of the pivot. This has never been obvious for me in my plane. For airplanes with a sight gauge, some look at the string and pivot when it starts flickering a certain way.

To learn how things feel in your airplane when it's time to pivot, you really need a knowledgeable person on the ground with a radio telling you exactly when it's time to kick. After that, it just takes practice to develop consistency.

Don't neglect the gyroscopic moment, which can be much larger than you may know. All RVs are not the same. The key variable between different RVs is propeller mass moment of inertia. The equation for the average moment is....

moment = mass moment of inertia x RPM x yaw rate

....so those with a metal Hartzell (high MoI) will have far higher gyro moments than those flying some lightweight composite prop.

The moment acts 90 degrees from the yaw input, in the direction of rotation. Viewed from the seat, our Lycomings rotate clockwise. Point the airplane straight up, get slow and start the hammer. If you kick right rudder, the nose will try to pitch forward. If you kick left rudder, the nose will try to pitch back, toward inverted.....which can be a significant physical contributor to the accidental inverted spin.

DanH said:

The equation for the average moment is....

moment = mass moment of inertia x RPM x yaw rate

Click to expand...

Unless you're a flight sim programmer, don't bust a gut with this.

In other words, you'll need a degree of forward stick during the pivot (right rudder hammers don't work well unless you have a Russian CCW-turning engine). You can mark a point on the horizon using the wingtip, and as you pivot, follow it and compare it to the position of your nose as it falls through the horizon in order to see if you're using the correct amount of forward stick to maintain the plane of the pivot.

To start with, when flying level, find a point on the horizon right on top of the wingtip. Mentally note how far below the horizon it is, and swing it around in front of the nose. Note how far this distance is above the top of your cowling. This will be the distance above your cowling the point you're tracking during the pivot should be. If the nose covers it up (or gets too close) as the nose swings through the horizon during the pivot, then you've used to little forward stick. If the gap is too great, you've used too much.

Also, as the pivot stops, look at your wingtip to see if you've ended up truly vertical in pitch. This is another indicator of the accuracy of the plane of rotation. Remember that gyroscopic effects are only at work while the airplane is yawing. As soon as the pivot stops, you'll need to immediately neutralize the forward stick, or you'll go slightly negative in pitch on the downline. Propellor torque is still strong after the pivot stops, so you'll still need right aileron for a moment before airspeed builds.

Stick movement when initiating the pivot will be right aileron followed by forward stick. It's a sequential movement, not a simultaneous one. Likewise, at the end of the pivot, it's the same sequence in reverse - remove the forward stick, then the right aileron. Use whatever aileron it takes to keep the wings 90 degrees to the horizon as the nose falls through.

After the pivot stops, look at each wingtip to see if you've stopped the pivot vertical in yaw as well. It's very common to over or under rotate the pivot and end up dragging a wing down...not that it matters unless you're striving for perfection, or being judged at an aerobatic contest.

A perfect hammerhead is a beautiful maneuver to watch, and one of my favorites. Such a simple looking maneuver, but so deceptively complex to get just right. Feels really good to hit one well.

Caution: glider hammerheads in an RV

hendrik said:

No experience in power planes. In the glider I look at the wing tip and start the pivot when the wind noise sounds about right. I never look at the ASI for that. Once I started the pivot, I keep my eyes at the horizon to check how much opposite aileron I need to keep the plane from rolling on its back (long wing span -> upper wing produces much more lift). When I'm almost through the turn I look straight down and check if I need to cheat and change the direction by a bit of roll during the vertical.

In a glider starting the pivot too early has a very similar effect to starting it too late. If I start too late, I'm too slow to make it all the way round, and the plane starts falling down sidewards until the nose drops down. If I start too early, the plane side-slips upwards, the tail acts as a vane preventing the plane from turning, I lose lots of energy until the plane is too slow and starts falling down sidewards.

If there is any danger of sliding backwards, don't let the controls go. You don't want them being banged into the stops by the reversed air flow.

Click to expand...

If you have a carbureted engine (no inverted fuel), you may find yourself doing exactly what is described above when the engine quits. Luckily when it happened to me/us (instructor induced), we still had some forward airspeed and full left rudder by both of us simulateously got the nose off the vertical. That sound of silence was a good indication of when to kick the rudder, but don't recommend this technique in an RV. Until I installed the inverted systems, would never go past 75 degrees vertical as a safety precaution. By the way, after recovering, the instructor put the RV in a moderate dive to try and see how fast it needed to rotate the wooden prop. That's when the student told the instructor what to do immediately!!!!!!! Starter is on the right.
Bill McLean
RV-4 slider