Descending Turns and Vne

[LousyFisherman]

So I finally get a day where the air is totally calm, like glass to port a water term. The perfect day to play around with training above Vma. Of course there is the fighter dive seen everywhere on TV. So I take the dreaded 150 up 8000' (4000' AGL), slow her down to 50 mph, prep and then execute a right hand slipping/descending turn. 400' feet later I'm doing 140mph and easing out of the dive, at 600 feet I'm level at 150-155 mph (Vne 160) and bleeding off speed.

My question is how did the WWII pilots control their speed because (rough numbers)
C150 gains 100mph/500' Vne of 150
WWII fighter gains (at least) 100mph/500' with a Vne of 450 mph (@10000')

This would imply that the pilot has to manage his speed very early in the attack and then is limited in maneuverability. Were the attacks along some form of log curve or parabolic curve? Is it just on TV? Is Vma much higher on these fighters relative to Vne than on GA aircraft?

TIA
LF

[iflyforpie]

I recall a story of a P-40 pilot (RAF I think) during the war that encountered a bunch of Bf-109s. Realizing that the only thing the P-40 did well was dive, he stood it on its nose and dove. One of the 109 pilots dove after him and passed him, giving a V sign as he went by.

The point is, most of these planes were so well built that they were only power and drag limited. It was only later when compressibility and control reversal became a concern.

[Colonel Sanders]

I have often thought that in a dive, if they wanted to
go faster, they should have feathered the prop

[PilotDAR]

Yes, Iflyforpie's point is the reason. A C 150 is an excellent plane, but there are things it cannot safely do, and it sounds like you were approaching one of them. Pointed down, most GA planes will easily exceed their Vne, and become very quickly very hazardous, even at idle power. Wings not level, or inverted makes it much worse. You might find that what you attempted actually met the CAR's definition of aerobatics. You will find a limitations placard in the 150, which reads in part: "No aerobatic maneuvers are approved, except those listed below:" A rolling break away is not among them.

What needs to be understood is that the entry to an "aerobatic" maneuver can appear fun and innocent, but as the maneuver develops, unexpected things happen, which might become rapidly unsafe. This is an underlying reason why spins are not approved in most GA aircraft. They enter fine, but the recovery can become alarming. Understand that these aircraft must all be capable of spin entry and recovery, but the recovery might require more than average skill and alertness.

Maneuvers which will take you toward inverted can become very unsafe, as all of your margins are gone. You probably had lots of speed to enter, and now you are there, you still have the speed, and you're pointed down gathering more, without a real plane to slow down. This is one of the reasons that the C 150 Aerobat has a faster Vne, to allow for these errors - but it still has approved maneuvers, and entry speeds, and a rolling break away is still no on that list! No hard feelings LF, just a word to the wise, the C 150 cannot do some things, and they should not be attempted. And, it gets worse with more sleek types (182 RG for my experience fooling around), they really build up speed fast, you gotta have a plan!

I've always wanted to do one of those rolling break aways, but have never flown and aircraft capable. I may have to go and prevail upon CS!

[Colonel Sanders]

What's kind of fun is a "split-S":

At a high altitude and slow speed, 1/2 roll from
upright to inverted, and pull through the 2nd
half of an inside loop, downwards. It's a neat
trick to play when you're doing a high-G tailchase
and you've run out of airspeed. Most people
don't like to follow it, especially at low altitude.


1/4 cloverleafs are great fun, too. Kind of a 1/2
barrel roll, split-S kind of thing.

Here's a full cloverleaf:

[AirFrame]

You will find a limitations placard in the 150, which reads in part: "No aerobatic maneuvers are approved, except those listed below:" A rolling break away is not among them.

You may have read the OP wrong... He said he slowed down, and then started a slipping turn to the right. That doesn't sound like an aerobatic manoeuver to me?

A "rolling breakaway" definitely sounds like something aerobatic, but i'm not sure what it would be... Can you describe further?

My question is how did the WWII pilots control their speed

In general, they didn't have to. The fighters were over-built to take the punishment of dogfighting done by relatively low-time, inexperienced pilots who were likely to jerk things around faster than a standard plane could take. All necessary when you're trying to avoid getting a keister full of hot lead, but gruelling on the airframe.

A few of the fighter pilots found out first-hand about compressibility as you approach Mach 1... Control ineffectiveness or reversal when you least expect it, ie. trying to pull out of a high-speed dive and the nose goes down, not up, when you pull back. That will definitely give you a need for a new pair of underwear. Getting close to the limits of your airplane, even in a controlled manner, can be exciting.

[iflyforpie]

What I do when I want to have some fun and trade altitude for airspeed is simply allow a spiral to develop. It doesn't take long on just about any aircraft to get into the yellow. Normal spiral dive recovery.... I'm pretty sure that doesn't count as an aerobatic maneuver since it doesn't involve any unusual attitudes or sudden maneuvers.

One way to keep the speed back is to keep the wing as loaded as possible. Pulling Gs is a very effective way of reducing airspeed.

Back to the warplanes.... they may have had published limits, but these were very overbuilt aircraft. The amount of battle damage these planes came back with was astounding. Names like Boeing, Consolidated-Vultee, Douglas, and Grumman would go on to leave post war legacies of building some of the strongest planes ever.... while lots of other manufacturers had to retire aircraft early due to structural issues (DH Comet, HS Trident, etc).

[cgzro]

The speed in a vertical-ish descending turn like that - a split S, builds up less if you pull aggressively so that the AOA is near stall and the drag is pretty high throughout, if you don't get the elevator working the speed will build up.

[PilotDAR]

You may have read the OP wrong... He said he slowed down, and then started a slipping turn to the right. That doesn't sound like an aerobatic manoeuver to me?

Well, I read:

slow her down to 50 mph, prep and then execute a right hand slipping/descending turn. 400' feet later I'm doing 140mph and easing out of the dive, at 600 feet I'm level at 150-155 mph

From CAR 101.01:

“aerobatic manoeuvre”

“aerobatic manoeuvre” means a manoeuvre where a change in the attitude of an aircraft results in a bank angle greater than 60 degrees, an abnormal attitude or an abnormal acceleration not incidental to normal flying;

If you have accelerated a C 150 from 50 MPH to 140 MPH in 400 feet, and continue to 155MPH in another 200 feet, going down, it was not a regular slipping/descending turn. It is a certainty that you had either or both of an abnormal attitude or an abnormal acceleration not incidental to normal flying.

Now I'm not specifically having at LF, though it might seem so (sorry LF - no personal attack intended). But I am using the report of an event, which I believe to be objective, and not contrived by me to illuminate an example, to simply remind pilots that maneuvers which are "iffy" to the limitations, or regulations, can lead to an outcome which might require abnormal pilot skill to recover, and the time to execute that recovery will become very short. I commend LF for giving us this report, that someone else might read replies, and think twice before exploring maneuvering beyond approved maneuvers. Limitations can be exceeded in small measure, but you really have to have everything else stacked in your favour while you're doing it....

[B52]

The definition of 60 degrees etc sounds familiar. It kinda gets forgotten about
when you do "unusual attitudes", that's the name that you use when you don't want
use another.

In aerobatics, they become normal attitudes and movements.
'notice the wing tip positions relative to the horizons, if I push the stick forward
notice how the nose goes 180 degrees to the left and aren't we having fun.

[Shiny Side Up]

Let me pull out my POH and see what it says...

Diving

Diving with pull-outs at required velocities and accelerations has been successfully demonstrated by the manufacturer of this airplane.

The theoretical terminal velocity of the airplane is approximately 475 knots indicated airspeed. It is not expected that this speed will be reached in service dives. Propeller at 45 degrees pitch.

The maximum allowable engine speed in dives is 3050 RPM.

Before diving, the following items should be checked.

1. Set propeller - 2100 RPM "Automatic"*
2. Blower - In neutral
3. Cowl Flaps - Closed
4. Mixture - Automatic Rich
5. Elevator Tab - 1 1/4 Nose down
6. Cabin Lock - Full open
7. After entering dive - Adjust throttle in accordance with tech note #23-40

* Aut. 14-206 (f) - Bureau of Aeronautics Manual directs that propeller be placed in positive high pitch prior to entering dives. However, if the procedure above proves satisfactory in service (ie, effectively prevents overspeeding) there is no objection to its ue. Most severe propeller control problem occurs when propeller is in "Automatic" and push over is made with closed throttle. If "Automatic" is used considerable power should be used during dive entry after which throttle may be set according to TN-25-40.

What follows in a nice little chart with angle of attack necessary to facilitate various degrees of dive angle. A ninety degree dive requires an AoA of -1.5 degrees.

Speaking of testing for said terminal velocity pull outs, I posted this once before, which I love reading about.

Airframe Strength

Grumman hired Carl Alber and me on the same day as its first full-time engineering test pilots. Carl had more hours than I, so he was selected for the first "bonus" demonstration job which was to try a terminal-velocity (vertical, full-power), 8G pullout test dive in the XF4F-8 Wildcat with the new 1350hp Wright R-1820-56 engine. He had never done such a dive, and his chase pilot had never seen one.

The only extra instrumentation for this one-flight Navy demonstration was a single-test accelerometer in the cockpit and the Navy V-G recorder installed behind the cockpit. These instruments would record airspeed and G-forces during the flight.

Carl climbed the Wildcat to 25,000 feet, rolled it over to vertical and held that angle to 8,000 feet. He then pulled slowly to be accurate on the G that he attained. He blacked out at 7G but continued to pull to what he thought was 8G. When he recovered, he found that the cockpit accelerometer had only recorded 7.2 G, so he climbed back to altitude and repeated the dive, pulling harder during the recovery. When he came out of his blackout, he saw the same "7.2G" on the accelerometer. On his third attempt, he decided to pull as hard and as fast as he could to attain 8G. After being blacked out for more than 30 seconds while the aircraft rolled all over the sky, he saw the same reading. During all this time , his chase pilot thought such antics were normal for this difficult dive.

Carl then decided there was something he didn't understand about terminal-velocity dives, so he landed and talked with chief test pilot Connie Converse about his problem. After he had parked the aircraft, the plane captain tried to fold the wings but couldn't. On investigation, they found that the wings were deformed so much that quite a few rivets had been pulled out of the main spar. The Navy V-G recorder was removed and checked; it showed that Carl had indeed reached the aircraft's maximum terminal-velocity speed and had recorded 9.5G, 11.5G and 12.5 G for the three dives! The cockpit accelerometer was then calibrated and found to have a bent gear cog that prevented it from recording past 7.2! This flight was two years before the invention of G-force suits that prevented pilots from blacking out in high-G pullouts.

The Wildcat's design ultimate, or breaking, load was 12G. During Carl's tests, the plane should have disintegrated in the air! Fortunately for Carl, its structure - and his - had been somewhat over-designed. Further inspection also revealed that the engine mount was also bent beyond repair.

In spite of these problems, the Navy accepted the demonstration flight as valid. The wing's outer folding panels were replaced, and with an new engine mount the aircraft was accepted for delivery! Carl then flew it to the new Genreal Motors Wildcat production plant in Linden, New Jersey, to be used for the experimental flights for the newer model FM-2 Wildcat. Before the end of the Second World War, General Motors delivered 4,437 of these extremely rugged Wildcats to the Navy.

Corwin H. Meyer - Flight Journal Magazine, February 2001

Fun stuff.

[iflyforpie]

They did not call Grumman the "Ironworks" for nothing.

[LousyFisherman]

First, PilotDar, I doubt you can offend me and if you did my attitude would probably be "What's with him today"

First test was what attitude do you need to fly a 150 at 159mph cruise? Lots of fun. 40 miles in 15 minutes wow!
Entries and exits were practiced in a progression from a simple forward dive and immediate exit through to rolling into the dive with a slipping turn, level and exit. The exit speed of 140 was chosen through testing.

The final attitude would have been close to what is defined "aerobatic" and I definitely define it as unusual. It was certainly over 45 degrees and I would guess somewhere around 60. I understand where the name "rolling break" came from. I really don't care about the legal limit, I doubt it is enforceable. My personal limit is: the first time I am in control when inverted I must have my instructor beside me At no time was there any danger of going inverted.

The mistake, attempting the slipping turn with the engine turning at 2000 rpm. I have no need or desire to do that again. immediately "Throttle back, level, exit, whew" .

LF, just a word to the wise, the C 150 cannot do some things, and they should not be attempted. And, it gets worse with more sleek types (182 RG for my experience fooling around), they really build up speed fast, you gotta have a plan!
I've always wanted to do one of those rolling break aways, but have never flown and aircraft capable. I may have to go and prevail upon CS!

Agree 100% with the "got to have a plan". See entry into diving turn with engine on above I was looking at the "Old Man's Aerobatics" course in the Colonels syllabus. Looks exactly like what I need.

What's kind of fun is a "split-S":
At a high altitude and slow speed, 1/2 roll from
.......
Cloverleaf.......

I must have misread the course description. sign me up for the "Really Old Man's Aerobatics" then, Colonel

I am using the report of an event, which I believe to be objective, and not contrived by me to illuminate an example, to simply remind pilots that maneuvers which are "iffy" to the limitations, or regulations, can lead to an outcome which might require abnormal pilot skill to recover, and the time to execute that recovery will become very short. I commend LF for giving us this report, that someone else might read replies, and think twice before exploring maneuvering beyond approved maneuvers. Limitations can be exceeded in small measure, but you really have to have everything else stacked in your favour while you're doing it....

I have little to no experience flying a plane where Vne has been a practical limitation. Just experiencing the difference between pushing forward vs rolling sideways to dive was invaluable. I think most of your concern is due to my poor communication of how much planning went into the exercise. As I mentioned the "aerobatic " definition is an "iffy" limit, it may have been exceeded. The Vne number on the 150 is a hard limit. It was never exceeded. The first time inverted rule is a hard limit, there was no chance it was going to be broken. My viewpoint is as long as no hard limits are broken it is a reasonable training exercise.

Where is the line between improving skills vs. stupidity. I actually think we agree on the basics of this, have a plan and don't go inverted without experience

It's funny, my personal limits and the capabilities of the plane never used to put these kind of constraints on my flying.

Shiny, if the colonel signs me off, can we go fly that plane you have the POH for? Make sure the O2 system works

LF

[PilotDAR]

My viewpoint is as long as no hard limits are broken it is a reasonable training exercise.

I'm going to differ a little on that one. Yes, if you did not break a limit, it was okay, but you might have put yourself into a phase of flight where breaking a limit was immanent without really skilled intervention - I've been there many times. Understand that a limiting maneuver (not a numeric limitation) may be imposed simply because it points you toward exceeding limitations, where the opportunity to get it right will be very limited. A loop, and roll in particular, fit into this description well. Spins are very close behind.

Here is an example of a spin (with inverted), which I flew as a part of certification testing. I practiced, and I had a plan. After 14 spins that day, I can attest that a Grand Caravan spins beautifully, but gives you NO room for error recovering. I never exceeded a limitation in the aircraft during the spins (other than simply spinning it to begin with - flight permit for that), but I did recover the resulting dive AT Vne, AND 2.8 G ('cause I took a G meter) and the peak rate of descent was 9200 FPM.



The limitations are specified for the aircraft to assure that it will not only be safe, but will always be pointed somewhere safe too!

[iflyforpie]

I know that when I want to go to a hard limit, I want it to be in a controlled fashion; a spiral or diving turn can get out of hand very quickly.

This winter, I had the rudder on the 206 repainted. Doing the static balance check, the rudder came in significantly more under balanced than was allowed. Talking with Cessna Support, I found that according to Cessna drawings the seaplane rudder had an under balance that satisfied the figure I had (silly me, I didn't check the balance beforehand ).

To be sure, I decided to take it up to Vne in glass smooth air and make sure that there weren't going to be any flutter issues. Rather than turn or peel off, I simply pushed nose down which would allow a slow buildup of speed and a rapid retreat should things get out of hand.

Of course, there were no issues forthcoming, but I would not have wanted to plow into a bad situation with an unproven aircraft.

[Colonel Sanders]

take it up to Vne ... make sure that there weren't going to be any flutter issues

If the aircraft was anything near what it was supposed
to be, there simply shouldn't have been any possibility
of flutter at Vne.

I might humbly point out that when you encounter
flutter, it can be explosive - the onset of it might be
so fast, and the flutter might be so violent, that there
might not be any time for you to do anything about
it.

A friend of mine, Andy Phillips, learned about rudder
flutter the hard way.

[photofly]

Doesn't FAR 23 broadly say that an aircraft should be free of flutter up to design dive speed V_D, with V_ne = 0.9 V_D?

[PilotDAR]

Doesn't FAR 23 broadly say that an aircraft should be free of flutter up to design dive speed V_D, with V_ne = 0.9 V_D?

Yes. This is one of the things I am required to test from time to time...

[iflyforpie]

take it up to Vne ... make sure that there weren't going to be any flutter issues

If the aircraft was anything near what it was supposed
to be, there simply shouldn't have been any possibility
of flutter at Vne.

I might humbly point out that when you encounter
flutter, it can be explosive - the onset of it might be
so fast, and the flutter might be so violent, that there
might not be any time for you to do anything about
it.

A friend of mine, Andy Phillips, learned about rudder
flutter the hard way.

Which is why I would rather find out about it on my own, rather than with a plane full of passengers, using the best data I had to ensure it was a complete non-issue.

[Strega]

I want it to be in a controlled fashion; a spiral or diving turn can get out of hand very quickly.

Really?

Mind you this sort of thing happens often nowadays... I guess pilots arent what they used to be with respect to actual flying skills...


http://www.liveleak.com/view?i=0c6_1389025127

[iflyforpie]

Why introduce risks that aren't required?

[Strega]

Why introduce risks that aren't required?

Flying is not required... and imposes risks, especially in GA..

[iflyforpie]

Very well then, why risk when there is no reward to the added risk?

[Big Pistons Forever]

I want it to be in a controlled fashion; a spiral or diving turn can get out of hand very quickly.

Really?

Mind you this sort of thing happens often nowadays... I guess pilots arent what they used to be with respect to actual flying skills...


http://www.liveleak.com/view?i=0c6_1389025127

The GA fatal accident rate in 1950 was 4 times higher than what it was in 2010. So yes I guess quote "pilots aren't what they used to be with respect to actual flying skills..." unquote; would be an accurate statement......

[Colonel Sanders]

The GA fatal accident rate in 1950 was 4 times higher than what it was in 2010

Given the advances since then to GA aircraft:

- nosewheel configuration
- electric start
- vacuum-pump powered gyroscopic flight instruments
- VHF comm radios, headsets, intercoms, boom mikes, PTT, ANR
- ADF
- VOR
- DME
- LORAN
- GPS
- database, moving map rnav ridiculously economical
- glass cockpit
- autopilots
- widespread implementation of Doppler radar
- internet communication of weather information, available everywhere
- ballistic aircraft chutes
- many decades of research into flight training

I'm a bit disappointed it's only dropped to 1/4

Even the ONE advance of wx information being available
via internet EVERYWHERE should have reduced the accident
rate to 1/4. In the bad old days, how you got aviation wx
was by phone, or by walking into an FSS and looking at
the maps and talking to a person.