Go try this in a real airplane, I suspect my formula will be dang close to what you get, descending in shallow rate of decent does not reduce load factor significantly.  On the initial push when you are changing the vector of the path, yes you'll unload some, but once in a steady state descend your acceleration rate will be steady (0) and your load factor will nearly be one if in a shallow decent (and nearly equal to a level turn if turning).

We do it at 400-500' AGL when circling at about Vy (120 KIAS).  Sometimes it's the only way to make things work and keep the field in sight when there's only a mile of visibility (which makes things really tight at that speed).

I'm not trying to sound like some expert pilot, and I don't want to start an argument with anyone, my whole point is that it's okay to bank an airplane low to the ground to make a turn work based on my experience freight dogging and I'll just leave it at that.

correct sir

Not trying to argue either, but there are several things in this thread that are just not correct (in terms of physics, math, and how airplanes fly) which lead to misconceptions.   I apologize as I did get a bit wrapped up in this, probably misread some things when I looked at the thread today, and as my wife reminds me of I probably came off sounding condescending.  

There is nothing wrong with an 180 AoB low to the ground if you have the energy and performance to support this, and as little as 30 degrees AoB can cause big problems in close if you are at wings level stall speed.  It depends, but how things work doesn't depend, it is what it is.

Two weeks ago I just did my first circle to land approach.  I was surprised that I was circling at 500' below pattern altitude and expected to stay 1.2NM from the nearest runway.

Yes I can see how that can get to be a very high performance maneuver in a faster aircraft.  For the DA40 I was in the 90 knot range, which is still over my personally set minimum maneuvering speed (80 knots and 30 degrees).

And here is the edit from my previous post which might have gotten lost as the discussion has progressed quickly.  

EDIT: In the video the discussion about bank angle conclusions starts at 1:20:50.  They concluded that private pilots should be comfortable with the required 45 degree spiral maneuver, and to make sure that the turn is coordinated.  They said that the amount of AOA needed is going to keep you away from the stall because you will not be trying to maintain altitude when making the turn and accelerating back to glide speed.  Load factor is what gets you to the stall.  But they recognize that a 45 degree bank will stall before a 30.  One pilot was expecting more benefit from 45 degrees than he saw.  They say you will learn your airplane and skill through testing.  A 30 degree bank will take more time, and time is a key factor in how much altitude you are going to loss.  You may be sinking faster at 45 degrees bank but you are doing it for less time so the net result is less altitude lost.  Aerobatic guys will tell you that if they want to do a quick reversal they will fly 70+ degrees, but that "no one wants to stick their nose out at 70 or 80 degrees of bank when they are only 500' above the ground."  The good compromise here is 45 degrees if you are comfortable with it.  One of the pilots was in a 172 doing 30 versus 45 degrees and getting 50' which with a 1:10 glide ratio would get you 500' closer to the runway.  But this pilot was also off in his testing by thousands of feet, so he concluded they were simply refining something that didn't matter.  Another pilot in the same airplane found that with 45 degrees she was making the runway, not just the airport property.  He said that you have to test and see if you are even close -- you are increasing your risk factor and through testing you will be able to determine if it even matters when you are missing other things like climb angle.  A short time later one comments that in his testing they were using a 4-5 second startle time, but if you go much longer you are actually giving up your chance to return because you are moving away from the runway at 100' a second.  Those are the notes that I jotted down just now while listening to that section again.

Which is why I set a minimum maneuvering speed.  I have heard of too many pilots getting close to stall speed on the base and final turns.

I listened to this section, they are saying the same thing I said.  In a descending turn less load is required to turn.  What they are leaving out it is not much less.  That was my point.  Charlie should have pointed that out.  Terry discussed the bunt.  Yes while you are unloading you decrease your load, but if you don't apply a load with the elevator you are not going to turn; again try this in a real airplane bunt in an AoB and see how fast you turn.  There is some transition while you are shifting from level to the decent where you are using God's g to help you around the corner, but this is momentary.  At 45 degrees AoB and 80 kts you are turning about 13 degrees per second, almost 14 seconds for 180 degrees, your not bunting or transitioning for that long a few seconds at best.

So why I am hanging on to all this.  I brought forth the argument that turn back is entirely possible, and it was (well in the conditions I tried them at, pattern altitude, keeping the prop set at max, idle selected, in my RV8 with the loading that I had).  My point was it depends, but one must understand that it will always depends and not something to just do one day because you read it on the internet; better to have an executable plan.  Misconceptions get started by things like this, both ways.  Same can be said for the video, if you take what Charlie and Terry said in terms of what most people understand (as demonstrated on here) you are safe in a descending turn to add AoB and not appreciably affect load factor, or stall speed.  Flying at best glide you'll likely never stall doing this, but if you try to stretch the glide (do not recommend this, as you can't get better than best glide) and find yourself slow and just assume you have the same margin you can very well be surprised.  I still haven't really answered my why question...In my time in aviation I have noticed that not all pilots understand how airplanes fly (not saying I did or do either), so we are taught based on some rules of thumb (remember when I said it depends), and not how airplanes fly; rules of thumb are much easier to teach.  Who wants to talk about math when flying?  Rules of thumb only work if you are within the assumptions the rules of thumb was developed on.  A good example is rule of thumb loose an engine after takeoff and go straight ahead, I was taught this, and never questioned it, until I was comfortable enough to come up with a better plan.  Not that I didn't think it was possible, but because I didn't think it was possible for me.  The explanation I gave for load in a turn was a mathematical formula that will represent what is actually occurring; try it with experimental data, it will follow the equation.  If you understand this and can apply it, then you can change your rule of thumb to your capabilities.  That is why I am hanging to it.

That is why circling approaches are so dangerous in anything with much power, and why they arent used in pt121 and a lot of pt135 operations.

The aqp grassroots defined minimum maneuvering speed is good stuff. Highly recommend looking it up on aviation101 or flight chops youtube channels.

I'm part 135, all of us turboprop guys hauling cargo that I've ever met use circle to land, otherwise we wouldn't be able to get into the small airports when it's IMC because that's all that a lot of these little airports have, circle off of a non-straight in VOR approach.  I don't know about Pt 135 outside of cargo, but I'd say my cohorts and I are a large portion of the part 135 world.  I only agree that it's dangerous if you don't understand your aircraft.  We were specifically trained for it at my company as it's vital to our operations to be able to do so.  I doubt the FAA would allow it in our SOP if they felt it was dangerous.

I get passenger Pt 121/135 no using circling, I wouldn't want to be a passenger in a jet doing a steep turn at 400' AGL coming in to land, but the boxes don't mind, lol

Yup that is what reinforced the concept and a put a name on it for me.  I had already been doing it on my own but it was good to know that it was a procedure in the commercial aviation world.

Regarding circle to land approaches, again yes they are an elevated risk, but can be executed safety if one remembers what they are in essence, which is a traffic pattern with a known entry point.

At one of the last operators to likely routinely execute CTL in US scheduled operations, we did so safely for decades, but they were rigorously taught in the actual aircraft, and not just the sim, where we all VOR 4L JFK CTL 31R.

As was pointed out, in smaller destinations, a CTL might be the only option, and as the Minimum Operational Network becomes reality, in a GPS degraded environment, might by the only option.

What you're describing seems to allude to the original certification of the 320 Laws, as well. Probably a function of the control laws making stalling nearly impossible in Normal Law, and the general selection of Load Factor versus AoA for pitch when in Normal Law.

Per Airbus, Vls is 1.23 Vstg (demonstrated flight stall speed) in clean configuration and represents a A/THR function. As you allude, its possible to fly lower than Vls, but is not a normal operation (dual A/THR failure being an event requiring a specific error in both FMGCs.)

While my current employer is good about demonstrating FPA flight at high AoA as part of our EET, functionally, we just don't use FPA in line flying, nor have seen other A320 operator ever use it, either.

I have successfully completed the maneuver twice.

The aircraft was a 1942 Taylorcraft L-2M with a Continental A-65 engine. These airplanes had very light wing loading.
I am certain the result would have been different in a Cessna or Piper single. (Excluding a Cub)

Thanksgiving day 1998. Calm winds, low humidity, air temp around 62 deg. 5100’ X 75’ paved runway.
I had flown from the grass strip I kept the plane hangared to the county airport to get fuel. I would strap a gas can in the back seat to minimize these trips.
After fueling I taxied to the active, did the run up, everything good.
Took off, climbing out just fine then the engine begins loosing RPM then just dies. It became very quiet!
I was about 300’ AGL. My first thought was to go straight ahead but I looked back (L-2M had a greenhouse with a cut down turtle deck) and estimated I could make it. Besides there was a field to my left if I didn’t.
I entered a fairly shallow left turn (maybe 15 deg.) careful not to get too slow. Ended up touching down about mid-field.
When I touched down, which was rather firm, the engine came to. I taxied back to the ramp and the plane ran like a watch. We tied the tail down and tried to make it quit. Finally just chalked it up to carb ice and got a ride home as I was done for that day.

The next day was a carbon copy weather wise, so I worked up my nerve and went to the airport.
Cranked fine, ran up fine, took off, climbing out, same exact thing!
I looked back, same scene as the day before, touched down a little shorter. Hit the ground, engine comes back to life!
At this point I’m about done with the whole flying deal!

Neither of the mechanics at the field could come up with a logical conclusion so I called an old gentleman who owned a grass strip in Virginia. If any body knew what was going on he would.
He told me to take the carberatur off and bring it to him. So I did.
He opened it up and asks “you been runnin car gas in this thing?”
I replied negative, but the previous owner did.
He asked “did he let it sit a lot?”
I replied positive.
He then showed me the problem. The old car gas had shellacked the inside of the carb. When the carb was tilted to a climb attitude the needle would stick causing it to flood itself out. He then tapped it with his hand and it broke free. That explained the engine coming back upon landing.
I have never liked the idea of car gas in planes, and will not run it in mine.

I then asked him how he knew that when 2 or 3 other mechanics had not figured it out.
He then told me about a 7AC Champ that had done the same thing to him about 20 years prior!

Great write up and glad you had a successful outcome. The sentence that stood out to me was that you were certain the result would have been different with a Cessna or Piper.

Another thing to add to this discussion is the real possibility of a rapid onset approach turn or cross control stall.

As MudEagle mentions, as there is usually a requirement for two turns for this maneuver...first, the 180 degree (plus), and second, a likely smaller alignment turn.

I taught students that the objective should be, if you execute this maneuver, a return to the airport "environment" and not necessarily the departure runway. The chances of survival in a clearway area are still far higher than a urban setting or dense forest.  

In practicing this maneuver, the tendency for even high time aviators to target fixate on the numbers versus just a soft area on the airport and cheat the nose/ground track with rudder was pretty real.

This is one of the many reasons I taught lots of slow flight in any extra time I had with students. For the civvies, its a really good skill for getting light aircraft into really tight fields (along with the forward slip to landing.) For the military guys, any 1 v 1 with two aircraft with a Thrust to Weight less than 1:1 will often devolve to horizontal scissors, and the aircraft/pilot with good slow flight skills will have the final turn to drop his nose and get the kill. It was one of the few tactically useful things we could teach in the T-34B, along with all the old A-4 and A-1 guys teaching toss bombing.

These are very good points.

I was especially conscious of keeping the nose down and almost fighting off the tendency to pull back on the stick during my situation.

Two things that are glaringly obvious to me with younger low time pilots today is apprehension of slowing down the plane and lack of navigational skills.
I don’t think enough time is spent on slow flight maneuvering and stalls/spins during primary training.
Fear of slowing down is one reason people fly B-29 size traffic patterns in their C-172 which is another opportunity for setting ones self up for being too low and slow to make the field should something happen.

Just describing Vls as you alluded that it is a proxy AoA, it is not an AoA gauge; but it does represent an AoA that one would want to avoid.  If you want an AoA gauge you can use the FPM relationship with the attitude to determine AoA (as this is all that AoA is).  You can also go into the maintenance pages to see the AoA.  Neither of which am I recommending, just pointing out that you can get AoA on the bus and many transport aircraft (it is a calculated AoA and not necessarily the true AoA the wing sees but is really close in most of the envelope the airplane is operating in).  Also, you can get below Vls in normal law, with the autoflight off you can decel past it; you'll get to alpha lock, then you can disconnect the power levers again, then you can slow to Vmin, at this point it won't slow anymore in normal law.  

Most don't use the FPM in the bus as it gets rid of the traditional FDs.  On Boeings it overlays on the PFD with the FDs remaining on the screen.  At AA folks would use the FPM on the bus. UA it is taught, but I doubt it is used often on the line.

In the "old Bus", we use FPA regularly on visual approaches.

I’ve rode on your Buses a bunch, but never up front oddly enough. I just ask for the “Airbus 80” and crash out on the F/A seats.

It’s dangerous, because when the engine failure happens, you are in a very low energy state, and suddenly confronted with dozens of variables, and not enough time to compute them.   Wind, density altitude, gross weight, other traffic, etc, etc.   I’ve flown a number of airplanes where it would be a possibility, at a certain point.  If not the same runway, then another runway or taxiway.   You have to remember, even Bob Hoover would have a couple seconds of “oh shit” delay.  In that time, he would put the nose to the horizon, and his brain would run through several pre calculated scenarios (because it should always be doing that in the background when you fly S.E airplanes.)

If you’re flying a plane like a PC12, or Maule or Husky, then it’s worth considering.   If you’re flying a standard recip, don’t try it, but do try to plan downwind departures, and constantly think about how you would do it.   Too much altitude and airspeed is just as problematic as not enough.

I like the idea of getting turned to downwind while continuing the climb on departure. Good idea.

In America pilots are trained on a "building block" approach.  Smaller to larger aircraft.

I trained on a prop, turboprop, then jet, now a jumbo.

You bet your ass the jumbo has a mandatory Vmma speed, but on the lighter aircraft we still had parameters to meet for things like maneuvering in a circle in certain configurations.  

Setting a minimum maneuvering airspeed is a good idea in GA, but in aircraft in general is almost more of a procedure.  

IMO, it should be taught as procedure in lighter aircraft too.

This is very solid advice.
I was trained this way 25 years ago and still practice this habit today.

Had the exact same thing with a 1340 a long time ago but it was the float in the carb.  Would run with the nose up but die when you put the nose down.  


As far as the turn goes?

Heavier, especially nose heavy planes act a LOT different with the engine off.  They turn into bricks.

Is this then the proper procedure?

Attached File

I like it!

Ha!

Never seen that illustrated!

Bored CFI with artistic talent and a long afternoon of bad weather is my guess. LOL

Still haven't done anymore experimenting, however got another data point.  The guy the gave me RV8 transition, the best guy out there and the most talented instructor I have ever flown with was giving rocket transition training to a friend of mine (his RV8 has full rudder pedals with brakes in the back).  Anyways, when they were doing engine out training he cut the power on him mid field down wind, my buddy extend a couple seconds then turned to land.  Well he made it but landed really long.  Instructor said let's try again but this time stay on downwind until you get to 500 feet then turn.  Tried and worked out perfect.  Not sure what their fuel load is but they both are big dudes probably at least 450# of people.   He said that is his number in the 8, if at 500 feet he can make a 180, otherwise somewhere in front of the wings.  So it depends.  When the weather gets better I'll give it a shot and see if I can get some good savvy data.