Disconcerting news...

[rv6ejguy]

Food for Thought

I was reading through an old copy of "Aerodynamics for Naval Aviators" here recently and found an interesting table illustrating the effects of bank angles on induced drag at a constant velocity- 100% at 45 degrees and 300% at 60 degrees. Stall speed increases by 41.4% at 60 degrees of bank. You can see why 60 degrees of bank at even 70 knots is a bad idea at low altitude.

 

[Gerald Clabots]

Gerry Clabots

This is the reason I installed a AOA sport in my 7A. I felt the most likely place I would get in trouble would be during the landing at a busy field by becoming distracted. The AOA sport give you a visual light bar indication plus a audable warning in your headset which does alert you to the situation.
Gerry

 

[Kevin Horton]

Look at the graph - as your angle of bank increases, so does your stall speed.

I was reading through an old copy of "Aerodynamics for Naval Aviators" here recently and found an interesting table illustrating the effects of bank angles on induced drag at a constant velocity- 100% at 45 degrees and 300% at 60 degrees. Stall speed increases by 41.4% at 60 degrees of bank.

I suspect both of the above posters know better, and simply got a bit sloppy with the words. So the following is for anyone else who might not be so sharp.

Stall speed is not directly related to bank angle. You can roll all the way around at zero g, and hence zero stall speed. For a given aircraft, configuration (e.g. flap angle, etc), and weight, the stall speed varies with the amount of lift being produced. If you are pulling 2 g, the stall speed increases to 1.41 times the value for one g, no matter what bank angle you have. You can have large bank angles with low g (and hence a low stall speed), and you can have small bank angles with high g (and hence a high stall speed).

In short, there is nothing wrong with a high bank angle on final turn, as long as you don't pull too much g. But, you must understand that if the g is too low for the bank angle you have, the nose will be falling. And, you can stall even at a low bank angle if you pull too much g.

Bottom line - on final turn, don't pull more g than is appropriate for the speed, flap angle, and weight.

 

[ChrisL]

Like in "Stick and Rudder" - you can't stall without pulling back on the stick. 20 Degrees bank and full aft elevator - BAD. 60 Degrees and neutral / slight aft elevators- Can't say GOOD for sure, but definately better than the former.

Love that book - it's timeless.

Chris

 

[rv6ejguy]

I suspect both of the above posters know better, and simply got a bit sloppy with the words. So the following is for anyone else who might not be so sharp.

Stall speed is not directly related to bank angle. You can roll all the way around at zero g, and hence zero stall speed. For a given aircraft, configuration (e.g. flap angle, etc), and weight, the stall speed varies with the amount of lift being produced. If you are pulling 2 g, the stall speed increases to 1.41 times the value for one g, no matter what bank angle you have. You can have large bank angles with low g (and hence a low stall speed), and you can have small bank angles with high g (and hence a high stall speed).

In short, there is nothing wrong with a high bank angle on final turn, as long as you don't pull too much g. But, you must understand that if the g is too low for the bank angle you have, the nose will be falling. And, you can stall even at a low bank angle if you pull too much g.

Bottom line - on final turn, don't pull more g than is appropriate for the speed, flap angle, and weight.

You are right Kevin, a bit sloppy on the wording. The operative wording was at a constant velocity- 2 Gs at 60 degrees. You're gonna have to add a ton of power or suck the nose way down to maintain speed at this bank angle. It is ok if you don't mind losing some altitude. If you don't do either, you WILL shortly stall. As I said in a previous post, you could unload the plane in the bank, again at the expense of altitude.

I'm not sure that pilots who are already going slow and start racking it tight are going to remember these finer points unfortunately.

It takes a pretty serious pull to get 2 Gs in my RV at say 70 knots- something should be screaming in your ear at this point that this is not something to be doing low and slow making the turn to final.

If people need a simple rule, keep the speed up, horizon somewhere in the windshield and the bank angles down- you can't stall it easily if you stick to this. Weren't we all taught this in flight school?

 

[Webb]

Sloppy???

Since this is the great land of the free and we have the ability to express ourselves. Here I go......

I disagree with sloppy. Perhaps casual but I was dead on.

An increase in stall speed is directly proportional to bank angle. As you increase your angle of bank, the load factor increases, vertical compenent of lift decreases and stall speed increases. It is independent of airspeed.

 

[PCHunt]

An increase in stall speed is directly proportional to bank angle. As you increase your angle of bank, the load factor increases, vertical compenent of lift decreases and stall speed increases. It is independent of airspeed.

That's only true if you maintain altitude when you are turning. And in actuality, it is Angle of Attack that causes a wing to stall. A wing will always stall at the same AoA, whether in a turn, straight and level, or upside down on the top of a loop. The control that directly changes AoA is the elevator. Pull back on the stick hard enough, and the wing will stall. Don't pull back, no stall. That's why the AoA gages are so good.

 

[tin man]

AOAs provide useful information, After 2000+hours in my RV I want to install one to see how it works. Aparently if you are a military pilot you need one. . An AOA WILL NOT compensate for poor pilot technique. If you need one to make a safe base to final turn then you need more training.
tm

 

[Webb]

That's only true if you maintain altitude when you are turning. And in actuality, it is Angle of Attack that causes a wing to stall. A wing will always stall at the same AoA, whether in a turn, straight and level, or upside down on the top of a loop. The control that directly changes AoA is the elevator. Pull back on the stick hard enough, and the wing will stall. Don't pull back, no stall. That's why the AoA gages are so good.

Pete, true about the AOA. However, notice that I didn't specify what the stall speed was. I was only refering to the stall speed would increase with an increase in bank angle. The vertical component of lift decreases with the increase in bank angle. Simple physics.

If we all back up to the origin of this topic, the accidents in the pattern were due mostly to stalls. My original guess was many were base to final when the speed was slow. Turn too steeply and not have enough airspeed to overcome the increase in stall speed due to bank angle.

A good example of this increase comes at the bottom of this website:
http://www.aerospaceweb.org/question/performance/q0146.shtml

Bottom line - Watch you airspeed when turning in the pattern. Low and slow is not the place to stall our birds.

 

[Kevin Horton]

Pete, true about the AOA. However, notice that I didn't specify what the stall speed was. I was only refering to the stall speed would increase with an increase in bank angle.

Sorry, this is a misconception.

The wing stalls when its angle of attack reaches the stalling angle. Angle of attack is controlled by the fore and aft movement of the stick. If you increase the bank angle, and you don't want the nose to fall, then you need to pull back on the stick to create more lift. It is the act of pulling back on the stick that causes the stall speed to increase, not the act of increasing the bank angle.

The stall speed depends on the amount of g you are pulling, not the bank angle. If you are at 1.5 g, the stall speed will be the same at 60 degrees of bank as it was at 0 degrees of bank (assuming the same side slip, engine power, etc for the two cases).

 

[hngrflyr]

A simple reason that pilots stall in the pattern is that many trim away most of the stick pressures. A few moments of diverted attention and an unconscious light tug on the stick and their precious airspeed has bled away to the point that if the pilot loads it up a little in the turn from base to final, the wing stalls. Every RV pilot should know that if he doesn't properly react to an unexpected stall, his next view over the nose will be the ground coming up to get him.

I don't trim in that manner for just that reason. If I become distracted from the task at hand, I would rather have the airplane speed up than slow down. If I'm too fast, I can deal with it. If I stall in that base to final turn there won't be enough altitude to deal with it.

 

[TankerBob]

Apparently this has turn into privates measuring contest about who knows better that who. So one final word and I am out.

NOTHING COMPENSATES FOR POOR TECHNIQUE! Nothing. And YOUR technique is not necessarily to ONLY or CORRECT way of doing something. You don't wanna use an AOA gage cause you have thousands of hours and are the best pilot in the world and that can fly circles around TG pilots in you ND airplane, FINE.

 

[hngrflyr]

For the most part, this has been a civil and worthwhile discussion. It is beginning to degenerate. I'll butt out too.

I am a little sensitive about this subject because I witnessed a stall spin accident that killed an acquaintance of just a couple of hours, that simply didn't have to happen. It really hits home to see your new friend laying on the ground with half of the face missing and no pulse. I was there within three minutes after they hit the ground. The friend was the passenger, not the pilot.

 

[rv6ejguy]

Fortunately something over 99.9% of flights don't end in a stall/ spin accident which means most pilots are doing the right things. Only a small percentage are not.

We are surmising that racking up the G in the final turn is getting many who do suffer this type of accident. I only hope that the discussion will sink into the many pilots who have read posts here and that they won't become of victim of this.

I really don't think many pilots who are fresh would actually make mistakes like getting too slow and turning/ banking/ pulling too tight without good reason. I would speculate that the reason is often time- fatigue. We've probably all suffered from it, made some mistakes and hopefully lived through them to learn that we should not put ourselves in that position again.

We come back to that self evaluation before a flight and an internal mental briefing on the circuit and how we will perform each phase. Maybe that sounds too scientific for many but it is proven to work. A mental checklist if you will.

I'm not a professional pilot but I strive to do things as well as I can and follow good practices like using checklists, rolling checks, sterile cockpit and doing cockpit briefings when two are aboard. I invite comments from other pilots when they fly with me. Am I getting sloppy? Is my friend getting too slow in the turn etc. I'll speak up and expect others to as well. My feelings won't be hurt. I'll be learning and I want to know to become a better pilot.

I am surprised when two pilots in one plane are involved in an accident- maybe they were both fatigued or maybe one didn't speak up when he should have.

 

[Webb]

I quit - this thread is all yours

I surrender to the nitpicking of the little point I was making. It's like asking for ketchup and you're told, no you want mustard. This thread has ceased to be fun - especially when the intent was to keep someones hind end from some serious runway rash.

Since I was called sloppy - let me be as explicit as I possible can.

An increase in bank angle is one possible way to increase the load factor and cause a stall. As we all know, an airplane can be stalled at any speed. The airplane?s stalling speed increases with proportion to the square root of the load factor. This means that an airplane with a normal unaccelerated stalling speed of 50 knots can be stalled at 100 knots by inducing a load factor of 4 Gs.

Perhaps the best explaination and discussion of what causes a stall was written by Barry Schiff in the book "The Profcient Pilot". In his own words, not mine - A stall occurs for only one reason: the pilot has tired to fly the wing at too large an angle of attack.

If it saves one person for stalling in the pattern, then this was a good thing. By the way - for a new (or any) pilot, Barry Schiff's book is excellent.

Good Evening - This thread is all yours. I'm talking my bat and ball and going home.

 

[garnt.piper]

Stall Stick Position

Hi all, I come late to this discussion, the pages were adding faster than I could download! I see some players have already left!

Eric Muller first wrote about the Stall Stick Position in his book 'Flight Unlimited' in the 80's, and it has been expanded on by others since, it is no secret, and is well proven. Simply put, the AOA is directly related to the fore-aft position of the stick, as Pete Hunt, Tankerguy and Ironflight allude to but don't quite mention. All Rv's, and other aircraft, therefore have a built-in AOA gauge - the position of the stick. Go out and try some stalls, note where the stick is relative to your leg. Remember this position, burn it into your brain. Go fast or go slow, pull some g upright or inverted, the wing will break with the stick in the same Stall Stick Position!! Note, it is the position that counts, not the stick force. You don't need to look at the ASI, or AOA gauge, or have a stall buzzer. Just don't move the stick aft of the Stall Stick Position. Fly an AOA approach sometime, and you'll see that the stick position is fairly constant.

Hope this helps.

 

[Kevin Horton]

I surrender to the nitpicking of the little point I was making. It's like asking for ketchup and you're told, no you want mustard. This thread has ceased to be fun - especially when the intent was to keep someones hind end from some serious runway rash.

I didn't mean to offend you, and if I did, I apologize.

 

[Ironflight]

Very Sad....

As a volunteer moderator, I don't get to see all of th threads all of the time - there is too much going on here at VAF! It is very sad when people get disgusted and leave a conversation - especially one in the SAFETY forum because people just feel that they have to be perceived as absolutely, 100% right on every word they write.....what sets the VAF forums apart from other online places is that we try hard to allow any and all Discussions to continue, rather than letting people just get into Arguments. If you have to argue with someone, why not write them a PM, rather than do it publicly? This is NOT a place to come pound your chest and show that you are the loudest guy on the block! It's supposed to be a lot more civil....

It's sad when an important safety topic ends up with people going off in a huff....

Just my opinion

Paul

 

[L.Adamson]

Simply put, the AOA is directly related to the fore-aft position of the stick, as Pete Hunt, Tankerguy and Ironflight allude to but don't quite mention. All Rv's, and other aircraft, therefore have a built-in AOA gauge - the position of the stick. Go out and try some stalls, note where the stick is relative to your leg. Remember this position, burn it into your brain. Go fast or go slow, pull some g upright or inverted, the wing will break with the stick in the same Stall Stick Position!! .

It appears that this subject fits into the "what causes lift, throttle/elevator for altitude, and lean of peak categories"!

My mind wasn't fully agreeing, so I googled in "stall & stick position". There is a lot of reading and controversy on this subject, as there is in my other examples.

At the end of the day, I won't say it's fact...

L.Adamson

 

[rv6ejguy]

Valuable Thread

I wasn't offended by Kevin's comments and I don't mind being corrected by anyone with the facts. Revisiting load factors, bank angles and stall speeds has given me a better understanding of all this.

3700 plus people have viewed the thread to date and hopefully learned something and reinforced things not to do in the pattern. If it prevents even one accident like this in the future, it was well worth some ruffled feathers IMO.

 

[Webb]

No apology needed

No I wasn't offended. Anger is a wasted emotion. What got my goat was the simple post I made that was called sloppy, a misconception, the poster knows better, etc... and it initially was:

"Look at the graph - as your angle of bank increases, so does your stall speed." I wonder if most of those accidents were base to final?

This casual comment turned into a splitting hairs discussion. If we were at the hanger and started talking the way some of the post were written, other pilots would have looked at us like "whose that moron". My comment could have even been more simple such as - "yea guys, keep that speed up when turning in less you want to stall your bird".

Funny part, everyone is right here - just trying to prove who was more right. Its like saying your going to get a drink of water....no you're getting some H2O.....no you're getting non organic compound composed of hydrogen and oxygen with the hydrogen bond being 90% electrostatic and 10% covalent..... Heck, I'll just go get a beer (no analysis of composition please).

On the very brightest side, it had huge numbers of readers. I truly hope that this one post prevents just one stall when slow and low. Definately makes one think - how can I prevent this from happening to me? If my point of increasing the load factor increases the stall speed makes everyone think about it when turning to final, then we all win and no one loses.

You folks are my flying bothers. Brothers get pissed at each other, fight, and go flying together. Heaven help an outsider that takes a poke at a member of the family.

I said I quit but felt I had to respond the the apology.

Remember what your teacher told you - "A good landing is one you can walk away from, a great landing is one you can use the airplane again." May all of you have great landings and with a little luck, they might even be pretty.

Later folks.
Webb
RV7A - N32WW

 

[flyeyes]

I wasn't offended by Kevin's comments and I don't mind being corrected by anyone with the facts. Revisiting load factors, bank angles and stall speeds has given me a better understanding of all this.

3700 plus people have viewed the thread to date and hopefully learned something and reinforced things not to do in the pattern. If it prevents even one accident like this in the future, it was well worth some ruffled feathers IMO.

Well said, Ross.

This is probably the most common reason people die in these airplanes.

One thing I suspect everyone who's posted could agree on is the need for practicing slow flight.

I'm not a CFI, but I would respectfully suggest that everyone should make flight (including maneuvering) at critically low airspeeds a regular part of their "routine." Go to altitude and fly a pattern at Vso + 5 knots. See what happens if you rudder around base to final and pull a little too hard (Hint: do this at high altitude because the answer is frequently a half snap roll).

I think it's also important do do this at aft (within limits) CG.

 

[USCANAM]

Thank You

As a high time pilot (6000 hours), and a low time RV9A pilot (22 hours) I think I have most certainly picked up some tips on this thread while doing my phase 1. Just because someone has written something doesn't mean that you have to accept it, but you certainly can think about it's merits.
Looking forward to flying off the next 18 hours so I can put some extra weight in the plane.
Regards
Jack
N99552

 

[flyeyes]

As a high time pilot (6000 hours), and a low time RV9A pilot (22 hours) I think I have most certainly picked up some tips on this thread while doing my phase 1. Just because someone has written something doesn't mean that you have to accept it, but you certainly can think about it's merits.
Looking forward to flying off the next 18 hours so I can put some extra weight in the plane.
Regards
Jack
N99552

Why can't you ballast the airplane during phase one? I certainly did.

You can buy 25# bags of lead shot from sporting goods stores that sell reloading supplies. They are useful for a lot of things, but I tend to worry that they would be dangerous in an accident.

My preference (and I may be entirely alone here) is big bags of dry dog food. They are reasonably easy to handle and can be strapped into the passenger seat. Bags of "play sand" from the home center work well also, but be careful that they don't leak abrasive sand into the airplane.

I would suggest adding 25# at a time in the baggage compartment on sequential flights until you reach Van's published aft CG limit or you feel uncomfortable with the handling (whichever comes first). If you stop before Van's limit, make that your maximum aft CG in your POH.

At first, large changes in CG will make it harder to land the airplane gracefully and cause significant handling changes (at least it did for me). By the time I had 100 hours in my RV, I hardly notice unless I'm paying attention to it.

Don't fly the same hour 40 times for your phase one....

 

[7mmSTW]

Views of a student...

Two things:

As a student pilot and RV wannabe I have enjoyed this thread. It helps to see the differing opinions experienced pilots have as well as provides a good oportunity for me to form my own at an early stage. Funny thing, I soloed on Friday and my first turn base to final, I thought of this thread and of the discussion here. All the while monitoring speed, bank and coordination while trying to keep my head as far out of the cockpit as possible. I really feel that everyone should go up from time to time w/ a safety pilot, block out all instrumentation and get back to flying a pattern by just plain flying the bird. Out of all patternwork I have done with my instructor this has been the most helpful. The one thing he keeps putting in my head, no matter what happens you've got to FLY the airplane. Everything else, speed, bank, coordination, amount of flaps to be used etc... falls into place if you do it right. Hope this makes sense to someone other than myself.

Secondly, as a law enforcement officer I feel that you should always be honing your skills. Modern training efforts in LE have improved vastly over the years. Simunitions and the like allow you to have been in a gunfight before you are really in one. How does this relate to my pilot training? It allows me to understand how to effectively view emergencies and emergency training as nothing more than fear inoculation so when I'm stressed enough that the "puppy dog brain" is trying to take over, I can say hey, I've been here before, allowing me to get myself out of a problem and more importantly recognize one before it becomes a true problem. Watching long time LEO's and long time pilots show the same to me, comfort and complacency tend to set in on many, not all. As only being in LE for three years I have already caught compacency trying to set up in myself and have to conciously fight it. I know the time will come when I will try to do the same as a pilot and hope that when that day comes I will recognize it before it's too late.

 

[USCANAM]

Why can't you ballast the airplane during phase one? I certainly did.
.

Thanks James for the suggestions.
Actually, by referencing to "extra weight", I meant a passenger, especially my wife who did after all let me build the plane full time while she was at work.
On the positive side, I can see how ballast in a -8 such as yours would be useful during phase one testing because of the much wider CG range that you will experience, as compared to side by sides such as the -6,-7,-9. I hope that -8 builders will take note of your suggestions.
Last week, I did have the opportunity to load up the baggage compartment in the 9A with about 85 pounds of my electronic scales when someone at a close-by airport (within my phase one range) asked me if I could weigh their plane for them. This gave me the opportunity to do some flying, and check the feel of a different c.g.. Actually, didn't even notice the difference, but was paying just a little more attention to airspeed on landing.
Thanks again
Jack
N99552

 

[pierre smith]

Sacrete as well...

Why can't you ballast the airplane during phase one? I certainly did.



Don't fly the same hour 40 times for your phase one....

....is a great way to add ballast. We borrowed an 80 lb sack and strapped it in vertically inside a garbage bag (to avoid spill) in Brian's -4. When it became time to take him for a ride in the back, his 100 lbs extra over the sacrete had little negative effect.

BTW, I'm am so glad to read so many good bits of advice and if this thread so much as saves one life, it will have been worth it. Furthermore, I'm letting you all know that whoever wants to come down here for a free review/BFR in my or your RV, I'm at your disposal until August, when I'm very busy dusting critters 'til the Fall.

Sincerely,