Spins

[flyguy]

There is NO " I REPEAT NO" recovery from an accelerated stall, co-ordinated or not at 100' agl! If I remember my old instructor right an airplane can be stalled at any speed with over zealous elevator control. Go up to 5000' and, if you can do it without references to the visual aid of the ground and runway, do one of your "tight patterns" then pretend you overshot the centerline of that runway and pull back real hard on the stick and watch the results! This is the stall that kills people on an otherwise normal pattern and approach to landing. I beg of you do not count on all the factors being in your favor if you stretch the envelope close to the ground! If you have any doubts go to the NTSB accident reports on approach to landing fatalities!

[Dave Clark]

I watched a Thorpe years ago do exactly that on a rushed turn to final to get down before the airshow. It killed both father and son as I recall.

Keep the ball centered, airspeed high enough and you can't get hurt. I've done some pretty steep turns to final that way.

[GAHorn]

I watched a Thorpe years ago do exactly that on a rushed turn to final to get down before the airshow. It killed both father and son as I recall.

Keep the ball centered, airspeed high enough and you can't get hurt. I've done some pretty steep turns to final that way.

No, No, No! Don't take this personally, Dave, but that's exactly what FlyGuy was just pointing out. You can stall an airplane at high speed! It's called an "accelerated" stall, and it's more common than intentional stalls when it comes to killing people in the traffic pattern.
Look at the 170 Owner's Manual, Operating Details Section, "Stalling Speeds" illustration. If an airplane stalls at 58 in level flight, it will stall at 82 in a steep 60-degree bank such as in a turn. Try doing that just over the numbers to claim your life insurance.
(CFI-hat on: Not trying to be the traffic-pattern nazi, but just so we all recall, it's illegal to perform manuevers not necessary for normal flight in the traffic pattern. Read FAR 91.303 (e) and the subsequent note. Traffic patterns serve a specific purpose other than positioning for landing. For the safety of all they are required in order that anyone observing the aircraft can anticipate that aircraft's next move, regardless of whether or not other aircraft are in the pattern. No waiver exists with regard to absence traffic. Hat off.)

[N1478D]

Well, those Cessnas and the like that make 747 size patterns sure are agravating. If everybody made nice tight patterns they would be easier to spot and the runway would always be within reach in case of an emergency. The 747 patterns at GA airports pushes everybody so far out that it is difficult to see them and very hard to anticipate when they are going to make their turns.

[GAHorn]

I agree, Joe! I'm not advocating 10-mile wide patterns. Or even 5 mile "corporate jet" patterns. Circling approaches require 1 mile visibility and that's an appropriate maximum for VFR traffic pattern downwind legs, in my view. (Otherwise a VFR aircraft could quite legally fly the pattern and yet be outside the view of an arriving IFR aircraft.) The minimum distance is dictated by the ability to descend from base leg to the runway at a reasonable angle. For a 170, that would be about 1/4-1/2 mile downwind, and turning base leg about 1/4-1/2 mile past the runway approach-end.
In your particular case, if you were already in the pattern when someone else arrives it would be a good idea for you to keep it in as close as possible. Otherwise anyone else would likely have to go around!

[dacker]

Just to add a little more info on accelerated stalls. Remember, a stall occurs when the critical angle of attack is exceeded, it has NO RELATION TO AIRSPEED. Say for instance if the critical angle of attack is 17 degrees to the RELATIVE WIND (I beleive that is about what it is in a 172) and you exceed that, regardless of how fast you are going you will stall the wing. This typically happens when heavy (higher AOA to create the needed lift), and with abrupt movement of the controls, which causes you to exceed the critical AOA.
If you don't believe me, just ask an OLD crop duster what happens when you try to make an abrupt pull up over those high trees at the end of the field when you still have full hopper on a hot day!
Thanks for letting me have a little CFI practice.
David Acker

[GAHorn]

That's correct, David! There were numerous dive-bomber pilots during WW-twice that joined their targets during abrupt pull-ups.
(Not sure about the 17 degrees, or how to determine that without expensive AOA equipment. So cheap little airplanes use airspeed indicators for a cheap substitute.)

[dacker]

17 Degrees was a number used by a fairly experienced fellow that in turn taught me, no idea whether it is correct, but the point is that each wing has a certain angle of attack after which it will stall whether it is an F-14 at 450 kias or a Sopwith Camel at 80.
O.K., enough aero from me, don't want anyone to fall into a coma while reading this!
David

[rudymantel]

David, I too have heard or read that 17 degrees is a typical stalling aoa for a light airplane.
Rudy

[flyguy]

The addition of increased c-force/load factor and the lessened relative wind in a steep turn are the forces that tears lift from the wing and cause accelerated stalls in the approach to landing situation. Nice "close-in" patterns are not always dangerous but those that leave little margin for turning final when a pilot has over-shot the runway, gather all these normally benign things into a bundle that has killed numerous occupants of poorly piloted planes. In the old Pilot's Handbook training material there are very descriptive drawings of how the stall speed increases with angle of bank. And show how angle of bank increases load factor as well as c-force. It is something every pilot should be able to recall instantly in a steep turn.

George listed the stall speed/angle of bank that are given in our Cessna poh. But the Pilot's Handbook of Aeronautical Knowledge, on page 25, shows higher numbers for a 60 deg. angle of bank. The factor is DOUBLE that of normal stall speed! And the BEAT GOES ON! From 60 deg. to 80 deg. the load factor goes from x-times 2 to an astonishing x -times 6 which is an almost impossible configuration in anything resembling general aviation airplanes! But a gen-av pilot trying to get back to the "numbers" might easily exceed his stall speed in that steep turn.

LANDING PATTERNS
Joe, the instructor I flew with gave a little memory enticement during pattern work. He placed of a piece of black electrical tape about halfway up the lift strut on my PA20, the high wing I got my ticket in, and showed how, at normal pattern altitude, that this put you about the right distance from the runway on downwind to make a good landing approach.

BTW almost all commercial planes land straight in from many miles away so there is no comparing ours with "747" patterns.

[N1478D]

BTW almost all commercial planes land straight in from many miles away so there is no comparing ours with "747" patterns.

Those 747's had to make a turn sometime to get on that long final. Some pilots make those kinds of turns at GA airports in GA aircraft, i.e. 747 patterns, but stuff happens.

Any bad maneuver that has you low and slow is running you out of options.

Like tight patterns, another fun thing to do is to practice touching down on the numbers. But, landing further down the runway is a safer option.

An accident waiting to happen is George removing his steps in a hope of gaining airspeed. Of course, the first time he forgets they are gone . . .

[zero.one.victor]

(Here's a trivia question: What's the difference between an "A and a "C" engine?)

George,I don't recall seeing an answer to this one. I think I used to know the difference,but now I can't remember.

Eric

[Dave Clark]

Yes Eric I started to write the answer then thought better of it. All I could remember that I think is correct is that they are indeed different engines. I think very few parts will interchange. Definately not the cylinders which can be identified by the shape of the intake ports (or is it the exhaust ports?).

Geez George it's been 25 years since I've built an A series so how 'bout enlightening us all?

[AR Dave]

I agree Joe, I could do 3 touch-n-goes while waiting for some of these pilots to bring their patterns back in the county. I told you about heckling one of them on the radio awhile back? "Hey are you sure you're on downwind for Russellville?" "I've only got 30 mins of gas left". Just a couple of witty cracks, you know. KRUE 122.7 is also broadcast on a loud speaker in front of the FBO / Airport, where the student pilot's instructor, nervous parents/grandparents, and everyone else I know, were all waiting for him to complete his first solo flight. Being new to the airport (and wanting to make new friends) and not knowing I was on loud speaker, I landed and went right over to find out what the party was about.

[N1478D]

I agree Joe, I could do 3 touch-n-goes while waiting for some of these pilots to bring their patterns back in the county. I told you about heckling one of them on the radio awhile back? "Hey are you sure you're on downwind for Russellville?" "I've only got 30 mins of gas left". Just a couple of witty cracks, you know. KRUE 122.7 is also broadcast on a loud speaker in front of the FBO / Airport, where the student pilot's instructor, nervous parents/grandparents, and everyone else I know, were all waiting for him to complete his first solo flight. Being new to the airport (and wanting to make new friends) and not knowing I was on loud speaker, I landed and went right over to find out what the party was about.

HA! Laughing again Dave, that has a lot of humor to it. Fell in to the same situation at GPM. After a few witty cracks, received a letter inviting me to the GPM Quarterly Airport Safety meeting. Went and listened to the FBO/Flight Training owner explain the differences in ability levels of students and others, etc. You can imagine the few emergency landing sites in the DFW area - a few football fields and WalMart parking lots. The thoughts of some of us was that, the wider the patterns, the more hours on the hobbs and in the instructors' logs. Some of the instructors seem to be teaching 747 patterns. They are way, way, further than gliding distance to the runway on downwind and base, sometimes they are out of sight. Then again, it's somewhat like when driving and the dirty sob that passes you is a speed demon and the idiot that you are trying to pass is someone who should not be allowed on the roads because they drive too slow.