An Almost Base-Final Turn Accident

[jason]

Jesse, this rubs me wrong a bit. Doesn't stall speed increase with bank angle? What are you saying here? I didn't get from the OP anything about an attempted skid.

Yes, increased bank angle does increase the stall speed. But the wing won't stall until it passes the critical angle of attack. There are many many factors that play into that angle.

Let's illustrate it another way. Let's say that you just lifted off of the runway. You have to clear the proverbial 50 foot obstacle so you pitch up to Vx and begin your climb. You maintain that airspeed by maintaining the proper pitch angle and power combination, right? So, you're still at Vx as you pass through 1500 feet AGL and all of the sudden your engine shuts down. What do you do? If you've ever practiced this with your CFI (which should have happened) you know that it requires an almost instantaneous push of the yoke to keep from stalling. You're decreasing your angle of attack by trading altitude for airspeed. If you failed to decrease the angle of attack a stall is almost assured. If that were to happen you wouldn't say "I stalled because the engine failed". The truth is that you stalled because you didn't trade one of the other resources that you had banked. There would be several ways to avoid the stall. Decrease your pitch, a sudden application of power, etc.

Jesse's point was that it wasn't the increased bank angle that caused the stall, but it was the failure of the OP to trade one of his other resources to compensate for the fact that he had to increase his bank angle. There are many ways to skin a cat. If it was absolutely imperative for the OP to increase his bank that much, then he needed to compensate in some other way.

 

[Kiloalphadriver]

"My primary CFI told me flat out that he didn't teach ground reference maneuvers (nevermind that I was 141)."

Really?? Wow!!

I can't stress enough how important it is to be able to fly a proper pattern based on a knowledge of ground ref maneuvers. Not only does it mean you're in control of the plane and your flight, but also for safety reasons.

(Stall-spin base to final, overshooting into a parallel approach, etc)

You can practice ground ref maneuvers (patterns) by yourself using roads as I described earlier.

I'm a strong believer in just because you're not a pro, it doesn't mean you can't conduct your flights like one.

If you can develop an understanding of what's happening to the airplane in the pattern, then you would no longer be surprised when you turn final.

Too bad we can't spend an hour or two in the air together, I would have you flying some pretty sweet patterns!!

 

[jesse]

Yes, increased bank angle does increase the stall speed. But the wing won't stall until it passes the critical angle of attack. There are many many factors that play into that

The key thing is that it only does do if you care about maintaining altitude.. If you don't, it does not.

If you cant FEEL the G forces of the increased bank then you're descending and your stall speed is fine.

Loading the wings, which is felt by increased G forces, increases the stall speed.

 

[dmccormack]

That's certainly true, but if you are skidding your stall speed goes way up and you'll get a really violent roll when you do stall.

I wouldn't suggest 'staring' at any one thing, but the ball is to me the most important instrument to scan turning base-to-final.

There's another thread today on a recent base to final fatal accident in Melbourne Florida that sounds like a stall/spin accident. Very tragic.

Anytime I see the ball on base to final it's deflected.

Then again, I like a slipping 180 to lose lots of altitude in a short distance.

 

[gismo]

Better advice would be "Don't stall."

Can't spin unless you stall.

Agreed. And if you stall completely at 200 AGL it won't matter if you're coordinated or not.

 

[spiderweb]

For those of you who are timid: do some aerobatic training.

If nothing else, it will teach you that the attitude of the aircraft is not necessarily related to AOA and whether or not you will stall.

 

[Geico266]

Only if you pull and attempt to maintain altitude. Let the nose fall and it won't increase the AoA. The problem is that the OP pulled for fear of banking more. It'd have been by far safer to just bank more while staying coordinated and not pulling more on the yoke.

110% agree.

 

[dmspilot]

A good technique for preventing a potential overshoot situation from arising in the first place has been recommended by Bill Kershner in his books. Make your downwind-to-base turn with a 30 degree bank and with a crisp roll-in and roll-out, and you'll have more time to judge the final turn, and will be able to use a shallower bank as well.

 

[denverpilot]

The "just play" can also be accompanied by stuff like, "Here, let me show you something, if you don't mind?... Okay cool... my airplane... Can you make it do... this?"

Not a "yee-haw, hey y'all watch this!" but something like "dutch rolls" or similar that are not "PTS" things to do, but that expand knowledge of how all the flight controls interact. Stick the nose to a point on the horizon while rocking the wings back and forth 30-45 degrees without turning. Now make the bank steeper. Hold altitude, but don't turn. Back and forth, back and forth.

(This one can be done to alleviate boredom on long cross-countries. Done right, and I mean really right... there's very little side-loading and someone in the back could sleep through it. They'd only know you were doing it if they opened their eyes.)

How the ailerons and rudder inter-play doing that, is a good experience if your feet aren't connected to your brain yet... as just one example.

The other that always made me laugh because I sucked at it, was one-wheel takeoffs. I don't tend to do those in my bird... I'll tear up a rental's tires if I want to go get good at that again someday...

There's a lot of learning how to control the aircraft "stuff" that isn't particularly dangerous or weird which isn't on any PTS list anywhere.

 

[dtuuri]

WRONG. The bank angle is NOT what caused you to nearly stall. You nearly stalled because you were AFRAID of banking more and instead of banking more you PULLED. The pull increased your AoA and nearly killed you.

This is something that IS NOT COVERED WELL by many instructors. Had you just banked more steeply, and just let the nose fall, you would have fixed rolled out onto final without an issue. If you didn't have the altitude to make this turn (which requires very little) you had already seriously screwed up and need to learn to fly the pattern instead of doing a rote routine and hoping it works.

Exceeding the critical angle of attack is what kills you. Banking and letting the nose fall does not increase the angle of attack. Banking and then pulling to tighten the turn does.

This is probably the most valuable thing I learned by watching my dad crop dust as a kid.

Let me make this simple. This is how you die:
- You realize you are going to overshoot final. You realize you're banked 30 degrees. OMG you can't bank more or you'll die (someone silly told you).
- So you want to tighten your turn. You pull some power, you cheat with a skid on the rudder, and you pull on the yoke to tighten it up
- The above action causes you to exceed your critical AoA and you go into a spin from your skid and die.

You will not die if you:
-Watch the runway as you're turning final. Bank to roll out on a perfect final. Perfect this. Become the master of it. If you need more bank, do it, but STAY COORDINATED and DON'T PULL. You're not a robot. The pattern is very dynamic. You need to make the airplane go where you want it to go. That means you don't just turn to defined angles and cross your fingers like most pilots do.

+1

Nicely said. Here's a caveat: Letting the nose fall, while not increasing AoA, increases radius of turn. There's no free lunch. The turn radius depends on AoA.

Personally, IMO, there's never a need to exceed 30° of bank in the pattern, especially for a novice.

Another thing: Nighttime straight-in approaches to airports are exceedingly difficult to judge. For IFR night circling approaches I always favored overheading the runway at a 90° angle and started out with the airport right below me.

dtuuri

 

[dtuuri]

I'm still working on getting the feel for the ball without looking.

Tip: Put the foot you don't need on the floor (flat). Just use one leg at a time and keep your heel on the floor.

Another tip: There's a present in your mailbox.

dtuuri

 

[gprellwitz]

If you want to get a good feel for the coordination and exploring the energy envelope, the commercial performance maneuvers really help. You don't need to be working on your commercial certificate to do them!

 

[mikea]

Thanks for the insight, CFI Jesse. It turns out I already knew some didn't realize....I've had some CFIs tell me I bank too hard in the pattern and a stall spin does scare me ta death but I always knew I knew my bird...

Now I realize I've always known to push on the yoke in the turn.

 

[poadeleted20]

Yes, increased bank angle does increase the stall speed.

No, it does not. The one and only thing which increases stall speed is increased load factor. I can put a plane in a 90 degree bank and have it not stall at all at any speed if I keep it unloaded, and I can have it stall at any speed at all wings level by pulling enough g (provided I don't rip the wings off before it stalls). This becomes a big issue in spin recoveries when folks have the wings level and the nose well down, and rapidly increasing airspeed -- it's pretty easy to be scared into pulling into a secondary stall well above "normal" (1g) stall speed in this situation if you're looking at a windshield full of ground instead of sky.

If we had AoA gauges in our planes, this confusioin would never occur.

 

[Banjo33]

What Cap'n Ron said. I couldn't get to the last post fast enough to point this out, but he beat me to it!

 

[wabower]

Earlier this week I rode with a pilot who made two L/H patterns to Runway 35 at two different airports on a day when winds were northwesterly ~15 knots and resulted in a tailwind on base. He overshot both base-to-final turns without realizing why, and was forced to do some unplanned maneuvering to regain center-line on final. Nothing particularly exciting, but interesting that he did it twice in succession. The final landing was right traffic, and the pattern was much better. I've ridden with him a few times and found him to be a competent pilot, just interesting to see this obvious chink in his technique.

We didn't talk about it at the time, but I plan to do so when we fly again.

 

[dmccormack]

I think some pilots get so fixated on the AWOS winds they ignore the possibility of different winds at 800-1000' AGL.

 

[jason]

No, it does not. The one and only thing which increases stall speed is increased load factor. I can put a plane in a 90 degree bank and have it not stall at all at any speed if I keep it unloaded, and I can have it stall at any speed at all wings level by pulling enough g (provided I don't rip the wings off before it stalls). This becomes a big issue in spin recoveries when folks have the wings level and the nose well down, and rapidly increasing airspeed -- it's pretty easy to be scared into pulling into a secondary stall well above "normal" (1g) stall speed in this situation if you're looking at a windshield full of ground instead of sky.

If we had AoA gauges in our planes, this confusioin would never occur.

Yes, Jesse already pointed out that I didn't clarify my statement well enough. Increased bank does increase stall speed IF you attempt to maintain altitude with nothing else changing. The increased bank angle will force you to pull back to maintain that altitude...which loads the wings.

 

[gismo]

Nicely said. Here's a caveat: Letting the nose fall, while not increasing AoA, increases radius of turn. There's no free lunch. The turn radius depends on AoA.

For example if you are in a level 30° bank the total force would be 1.155g and the lateral force would be 0.57g. If you increase the bank to 45° without increasing AoA (maintaining the 1.15g load) the horizontal force rises to .82g or 82% of the lateral force in a level 45° bank. IOW the turn rate only goes up a little over 56% of what you'd get in that 45° if you held your initial descent rate. You'd also get the same turn rate by banking 39°.

There are other undesirable consequences of maintaining AoA as you increase the bank. When you fail to increase lift to maintain the initial descent rate as the bank angle is raised, the airplane will accelerate towards the ground. Increasing bank to 45° from 30° while letting the nose drop to maintain 1g loading leaves you with your VSI increasing 350 FPM for every second you maintain that condition (1000+ FPM in 3 sec). Of course some of that increase shows up as additional airspeed which helps with the stall margin but that also increases the turn radius. And at some point you will need to arrest the extra sink rate which requires pulling more g. Like you said, no free lunch.

 

[Henning]

Your situation is exactly why I like and how I use my G-500 430w. Down low VFR with an IFR ability (unused except for IPC which smoked along just fine,) I could use the nav; lead in arcs displayed and all, I can fly it down low with confidence so long as I have a few miles vis.

 

[Witmo]

For example if you are in a level 30° bank the total force would be 1.155g and the lateral force would be 0.57g. If you increase the bank to 45° without increasing AoA (maintaining the 1.15g load) the horizontal force rises to .82g or 82% of the lateral force in a level 45° bank. IOW the turn rate only goes up a little over 56% of what you'd get in that 45° if you held your initial descent rate. You'd also get the same turn rate by banking 39°.

There are other undesirable consequences of maintaining AoA as you increase the bank. When you fail to increase lift to maintain the initial descent rate as the bank angle is raised, the airplane will accelerate towards the ground. Increasing bank to 45° from 30° while letting the nose drop to maintain 1g loading leaves you with your VSI increasing 350 FPM for every second you maintain that condition (1000+ FPM in 3 sec). Of course some of that increase shows up as additional airspeed which helps with the stall margin but that also increases the turn radius. And at some point you will need to arrest the extra sink rate which requires pulling more g. Like you said, no free lunch.

Thanks for the math. This is why I think its dumber than dirt to tell someone that's overshooting the base to final turn at night to bank steeply but don't increase the wing loading. Your sink rate jumps up, your turn rate doesn't increase all that much, and you end up crashing short of the runway; but at least you weren't stalled or in a spin.

 

[Matthew]

At our glider club meeting yesterday we watched a video produced by the Soaring Safety Foundation. They used Condor, which is considered 'THE' flight simulator for gliders.

There are several videos, each showing a different accident scenario. One is the base-to-final spin. It's interesting to watch and see how it can happen, from several different vantage points.

It's a .wmv file, so instead of attaching it, I'll have to link to it. It's on this page, and it's called "Stall/Spin base to final" (it's the last one).

http://soaringsafety.org/school/badvideo.html

 

[jesse]

Thanks for the math. This is why I think its dumber than dirt to tell someone that's overshooting the base to final turn at night to bank steeply but don't increase the wing loading. Your sink rate jumps up, your turn rate doesn't increase all that much, and you end up crashing short of the runway; but at least you weren't stalled or in a spin.

Now you're just being ridiculous. You're not going to crash into the ground. You have a gain in airspeed and you just made a crisp turn that didn't take much of any time to complete. You can increase wing loading to some degree with your newly discovered airspeed. You can always increase thrust to sort things out as well. His entire problem is flying the pattern by a rote set of instructions.

You won't even get to 45 degrees because you're eyes are on your target and you're coupling the ailerons to roll the airplane onto that target. This isn't a game of math, it's a game of feeling the airplane.

Notice the 56% increase in turn rate. That's pretty significant. This turn does not take much of any time if you do it nice and crisp.

 

[Geico266]

Yesterday, while attending a local b-fast I did a few tight turns while dropping the nose. While this is nothing new for me I thought I would pay attention to the numbers more. It was interesting in the airspeed remained the same and the turn was 60 degrees. It was tight and I pulled it a little tighter. Fun stuff.

I think the point of this thread is tohave been situational awareness. The OP should have know the runway winds 25 miles out. He should not have been paying with the GPS to find the winds in the pattern. He should not have been flying at night without currency.

Lesson learned. Analyze, improve, implement changes. Move on.

 

[Everskyward]

I task my passenger with helping to locate the field while I divert a little attention to GPS groundspeed vs. airspeed to help determine wind direction for landing.

How does this help determine wind direction for landing?

Radio chatter at a nearby Class-B is issuing instrument approach clearances to the south, but groundspeed indicates that my landing should be northbound. My passenger spots a landmark that I know well and I trace my eyes from there to locate home.

I attempt a straight-in approach to the north runway from 500' above pattern altitude and quickly realized that it's not going to work. A sidestep puts me on downwind for south landing 200' below pattern. Groundspeed confirms that I passed through a shear layer.

Good lesson to learn here. The winds aloft don't necessarily correspond with the winds on the surface so you can't depend on your GPS to tell you what the winds at the surface will be.

My eyes are glued to the runway for over-concern of losing position and orientation.

I think this was a big part of your problem. It's easy to get tunnel vision, especially if you are stressed. It's also very common. Because you were looking for the runway you neglected other things.

 

[Tracey]

Lesson learned. Analyze, improve, implement changes. Move on.

Good advice.

 

[Jaybird180]

If you want to get a good feel for the coordination and exploring the energy envelope, the commercial performance maneuvers really help. You don't need to be working on your commercial certificate to do them!

This is on my 'to do' list.

 

[Jaybird180]

How does this help determine wind direction for landing?

Good lesson to learn here. The winds aloft don't necessarily correspond with the winds on the surface so you can't depend on your GPS to tell you what the winds at the surface will be.

I think this was a big part of your problem. It's easy to get tunnel vision, especially if you are stressed. It's also very common. Because you were looking for the runway you neglected other things.

I too am in similar situation. My home field is tough to locate at night and there is no Wx reporting to give landing indication. Windsock......fuggedaboutit. I take a guess with GPS too. I have also landed with a tailwind a time or 2....don't want to do many of those.

 

[poadeleted20]

How does this help determine wind direction for landing?

I suppose one could do a 360, and note the direction in which the GS was lowest, but that only tells you wind at altitude, and...

The winds aloft don't necessarily correspond with the winds on the surface so you can't depend on your GPS to tell you what the winds at the surface will be.

 

[gismo]

Now you're just being ridiculous. You're not going to crash into the ground. You have a gain in airspeed and you just made a crisp turn that didn't take much of any time to complete. You can increase wing loading to some degree with your newly discovered airspeed. You can always increase thrust to sort things out as well. His entire problem is flying the pattern by a rote set of instructions.

You won't even get to 45 degrees because you're eyes are on your target and you're coupling the ailerons to roll the airplane onto that target. This isn't a game of math, it's a game of feeling the airplane.

Notice the 56% increase in turn rate. That's pretty significant. This turn does not take much of any time if you do it nice and crisp.

Jesse, while I completely agree that if you don't pull as you steepen a turn you won't increase the stall speed but from every angle I've looked at this, this technique does not result in a shorter turn unless you have altitude to lose (safely). I do believe that you can make a 1.15g 45° banked turn with less radius than with a 30° bank with the same loading but the difference isn't 56% because the extra airspeed increases the turn radius significantly (radius is proportional to the square of the airspeed) and you must complete the turn high enough to arrest the sink without stalling. BTW the extra speed doesn't help with the pullout either because leveling out is flying a curve in the vertical plane and IIRC the radius of that arc is independent of airspeed (assuming you load to max AoA for the airspeed) because both available lift (g force) and radius with constant lift increase in proportion to V^2.

Bottom line is that if altitude loss doesn't matter you can indeed make a sharper turn without increasing the AoA or loading by increasing bank without pulling back but for any significant decrease in turn radius the resulting altitude loss is significant so it's not always going to be a useful option on a base to final turn. OTOH, I've nothing against giving pilots another tool in the bag as long as you teach the limitations along with the technique.

 

[Henning]

Exactly, you have to pull Gs to change your inertial path, end of story. Do you have the energy required? That's the thing you get unloading the wing is that you'll store energy from gravity as quickly as possible since you aren't converting it to lift while being able to reorient the airframe for the upcoming shift in ballistic trajectory free from stall effects. The obvious problem here is that you need either an upward ballistic trajectory or altitude to give up.

 

[redtail]

This thread is very educational. As a low time pilot never having banked more than 45* while practicing steep turns, I really want to get the feel and broaden my knowledge of the envelope. As such, I've just signed up for an aerobatic flight next month out on Long Island. I'm starting to think that the FAA should require much more than what we were given in basic flight training!

 

[gismo]

The obvious problem here is that you need either an upward ballistic trajectory or altitude to give up.

Good point. For some reason I hadn't considered using a wingover to make the base to final turn tighter but performed correctly it might work.

 

[Henning]

Good point. For some reason I hadn't considered using a wingover to make the base to final turn tighter but performed correctly it might work.

It does, even in a 310 with a 25' 180kt pattern entry...

 

[bbchien]

Jason, you still had too much information in the photograph. I can see the turn and bank.
So instead, I use a blanket.

 

[jesse]

Jesse, while I completely agree that if you don't pull as you steepen a turn you won't increase the stall speed but from every angle I've looked at this, this technique does not result in a shorter turn unless you have altitude to lose (safely). I do believe that you can make a 1.15g 45° banked turn with less radius than with a 30° bank with the same loading but the difference isn't 56% because the extra airspeed increases the turn radius significantly (radius is proportional to the square of the airspeed) and you must complete the turn high enough to arrest the sink without stalling. BTW the extra speed doesn't help with the pullout either because leveling out is flying a curve in the vertical plane and IIRC the radius of that arc is independent of airspeed (assuming you load to max AoA for the airspeed) because both available lift (g force) and radius with constant lift increase in proportion to V^2.

Bottom line is that if altitude loss doesn't matter you can indeed make a sharper turn without increasing the AoA or loading by increasing bank without pulling back but for any significant decrease in turn radius the resulting altitude loss is significant so it's not always going to be a useful option on a base to final turn. OTOH, I've nothing against giving pilots another tool in the bag as long as you teach the limitations along with the technique.

Yes you will give up some altitude but you also have excess thrust to deal with that issue. Bottom line is if you're about to blow through final you already ****ed up and if you'd just watch the runway and bank whatever you need in the first place you wouldn't overshoot.

If you don't have the altitude to steepen your bank something is seriously wrong, people that fall into this spin trap had the altitude but chose to ignore that option. Their fear of the ground is what causes them to spin into it.

We are saying the same things it's just that you haven't watched pilot after pilot struggle with the base to final turn as you sit on the right seat bouncing around the pattern all day.

To sum this up -- you do have the altitude to spare, steepening the bank will help, and if you fly by looking out the window versus a rote procedure you won't fall into this trap in the first place.

 

[Jaybird180]

To sum this up -- you do have the altitude to spare, steepening the bank will help, and if you fly by looking out the window versus a rote procedure you won't fall into this trap in the first place.

OP said he never referenced any instruments. So I disagree with your proposed antidote.

Looks like simple task overload to me.

 

[Henning]

OP said he never referenced any instruments. So I disagree with your proposed antidote.

Looks like simple task overload to me.

...due to basic inability.

 

[jesse]

OP said he never referenced any instruments. So I disagree with your proposed antidote.

Looks like simple task overload to me.

If the OP had looked out the window and flew the airplane he would have never had the problem in the first place.

 

[Jaybird180]

Here we have an opportunity from a guy who confesses after a scare and what happens here:

People trash his CFI
Trash his basic skills
Argue theory as though they were in the cockpit with him

I see very little offered to this guy in the way of encouragement. For all we know he could be the next aviation walk-away with the seed of the next Bob Hoover with proper encouragement, training and time.

Shame. Sorry I don't have more answers at this time.