When do you slowdown to VA

IRT the Airbus crash - I think I remember the Feds saying something in the Aftermath along the lines of "OK, at Va you can deflect ONE control fully and not break the airplane. No fair stomping rudder AND yanking and banking." It's possible my quote isn't an exact replica. . .I've had it in my head that elevator deflection at/below Va was the important input in GA aircraft - so as to stall the wing before breaking it?
 
Sundancer said:
IRT the Airbus crash - I think I remember the Feds saying something in the Aftermath along the lines of "OK, at Va you can deflect ONE control fully and not break the airplane. No fair stomping rudder AND yanking and banking." It's possible my quote isn't an exact replica. . .I've had it in my head that elevator deflection at/below Va was the important input in GA aircraft - so as to stall the wing before breaking it?
Click to expand...

Va has always been the maximum airspeed one control can be rapidly fully deflected in one direction. It was after A300 accident that the industry realized pilots weren't being taught about it correctly.

NTSB said:
During this accident investigation, the Safety Board learned that many pilots might
have an incorrect understanding of the meaning of the design maneuvering speed (VA) and
the extent of structural protection that exists when the airplane is operated below this
speed.

From an engineering and design perspective, maneuvering speed is the maximum
speed at which, from an initial 1 G flight condition, the airplane will be capable of
sustaining an abrupt, full control input limited only by the stops or by maximum pilot
effort. In designing airplanes to withstand these flight conditions, engineers consider each
axis (pitch, roll, and yaw) individually and assume that, after a single full control input is
made, the airplane is returned to stabilized flight conditions. Full inputs in more than one
axis at the same time and multiple inputs in one axis are not considered in designing for
these flight conditions.

The American Airlines managing director of flight operations technical told the
Safety Board, during a postaccident interview, that most American Airlines pilots believed
that the airplane would be protected from structural damage if alternating full rudder pedal
inputs were made at an airspeed below maneuvering speed. . The American Airlines A300
fleet standards manager confirmed this belief during testimony at the Board’s public
hearing for this accident.
Click to expand...
 
Dan Thomas said:
It sounds like we really need to consult the FAA for the official definitions of Va and Vno.

View attachment 117307

View attachment 117308

https://www.faasafety.gov/files/notices/2015/Nov/V_Speed_Review.pdf

How quickly we forget our training....
Click to expand...
Nobody forgot that, but in all honestly that is legal speak clear as mud.

You could be flying along in perfectly smooth air, then get a good jolt.
Most here have likely experienced that.
How does that fit into the definitions?
How does that answer the OP’s question?
 
Dan Thomas said:
FAR 23 airplanes are stressed to 3.8G positive. Engine mounts are stressed to 9G positive. They want that engine staying put in a crash. You're not likely to tear it off by yanking on the elevator.

Some airplanes have a habit of failing the horizontal stabilizer before the wing. The Cessna 210 and Bonanza have done that. A VFR pilot flies into IMC, loses control, and pops out of the bottom of the cloud and finds himself spiralling nearly straight down at or over Vne. He pulls back and fails the stab and elevator, and the airplane tucks forward over onto its back and the wings fail in negative G loading.
Click to expand...

What’s the way of recovery with failing the horizontal stabilizer?
 
sarangan said:
V-g diagram is your friend. This from PHAK.

Basically, below Va you can't cause damage to the airplane regardless of control input. As for when you should use Va - any time you feel the airplane is being bounced around that is equivalent to full control deflections. That would be fairly rare except in severe turbulence. Unable to accurately turn the radio knobs is not that.



View attachment 117309
Click to expand...


Your VG diagram is incomplete because it lacks the load factors for turbulence. Being at or below Va means you can move a single flight control, in one direction, one time and in smooth air without damaging the airplane.



Add turbulence or multiple flight controls, or multiple movements of one or more flight controls you can damage the aircraft.

This is why in turbulence is it recommended to maintain attitude and accept changes in altitude.
 
Last edited:
Albany Tom said:
How is that at all helpful?
Click to expand...
If the crosswind vector component is so great that the airplane would land in a crab, despite max crosswind slip ie there is no more rudder effectiveness to straighten out, then landing faster will give you more rudder effectiveness. The other thing is you can decrease the relative cross wind vector component by landing on a diagonal to reduce the angle.
 
Last edited:
mandm said:
What’s the way of recovery with failing the horizontal stabilizer?
Click to expand...

I'd imagine the Emergency Procedure would be something like:
- Verify Loss Of Elevator Control
- Verify Loss Of Elevator Trim
- Since You Have Now Lost Your Ability To Aviate Or Navigate,
Consider Letting ATC Know Your Approximate Return To Earth Location
- Prayer Optional
 
Dan Thomas said:
FAR 23 airplanes are stressed to 3.8G positive. Engine mounts are stressed to 9G positive. They want that engine staying put in a crash. You're not likely to tear it off by yanking on the elevator.

Some airplanes have a habit of failing the horizontal stabilizer before the wing. The Cessna 210 and Bonanza have done that. A VFR pilot flies into IMC, loses control, and pops out of the bottom of the cloud and finds himself spiralling nearly straight down at or over Vne. He pulls back and fails the stab and elevator, and the airplane tucks forward over onto its back and the wings fail in negative G loading.
Click to expand...

1. Pilot loses control in IMC.
2. Is in a spiral nearly straight down over Vne.
3. Pilot attempts a recovery by pulling back on the elevator.

The airplane at this point doesn't have a habit of doing anything other than coming apart when the pilot executes an improper recovery from an extreme unusual attitude. The wing failing or the tail failing really makes no difference to the outcome of the event. The design limits of the aircraft were exceeded both by velocity and G loading.
 
Last edited:
Clip4 said:
Add turbulence or multiple flight controls, or multiple movements of one or more flight controls you can damage the aircraft.
Click to expand...

I think this is a key component - multiple control inputs on a stressed airframe. I was at a formation flying clinic with Doug Rosendahl 20+ years ago and he was talking about aerobatics and explained the math behind "pull OR roll, but not both" and how trying to roll on an already G-loaded airframe increases force drastically (maybe exponentially?) on the wing. I can't remember the exact calculations on it, but it was scary enough to know that I now fight turbulence (and fiddle-farting around in the practice areas) one control input at a time.
 
Albany Tom said:
For the OP - did you have turbulence the whole way, or just on the first third or so of the flight from GF over the Berkshires into central MA? I wasn't flying yesterday, but asking because I do flights similar to that from time to time.
Click to expand...

The worst of it was definitely crossing the berkshires we started at 5500' which I suspected would be too low as it was a somewhat gusty day. 7500' was much smoother contemplated 9500' but by then we were almost to ORE and it was smoothing out a bit by the time we got to ORH it was no factor.

So the short answer to your question the first 1/3 of the trip was the worst and was still doable. None of the stuff on the floor ended up touching the ceiling, and no heads made impact with the ceiling either (like they did on my wifes 1st XC trip with me in a rental 172 LOL)
 
MajorTurbulence said:
Not understanding. Do you mean that our aircraft are certified to one set of force limits, but in actuality, those limits are higher than certified ie our aircraft are overbuilt structurally? Good to know, but who of you want to test that hypothesis to its conclusion without a parachute and enough altitude to deploy it.
Click to expand...
Good luck getting out of piper Mooney bonanza with the door on the wrong side and a seat/yoke in the way!
 
Randomskylane said:
Good luck getting out of piper Mooney bonanza with the door on the wrong side and a seat/yoke in the way!
Click to expand...
Totally right. Would likely need some centrifugal force or gravity assist to propel you out the passenger door. Pulling yourself out might be difficult!!

Hats off to the test pilots who must have a plan, like emergency hinge pin pulls on the doors etc.
 
Sundancer said:
I've had it in my head that elevator deflection at/below Va was the important input in GA aircraft - so as to stall the wing before breaking it?
Click to expand...

That's right. The wing will stall when it reaches 3.8G at Va.

dmspilot said:
Va has always been the maximum airspeed one control can be rapidly fully deflected in one direction. It was after A300 accident that the industry realized pilots weren't being taught about it correctly.
Click to expand...
If I recall correctly, it was a left-right full rudder event. The fin is stressed in one direction, bending it somewhat, then it's suddenly thrown the other way, with more travel due to the first deflection. It fails.
guest user said:
I'd imagine the Emergency Procedure would be something like:
- Verify Loss Of Elevator Control
- Verify Loss Of Elevator Trim
- Since You Have Now Lost Your Ability To Aviate Or Navigate,
Consider Letting ATC Know Your Approximate Return To Earth Location
- Prayer Optional
Click to expand...
Wrong order. Prayer first. Might not have time for it otherwise.
Clip4 said:
1. Pilot loses control in IMC.
2. Is in a spiral nearly straight down over Vne.
3. Pilot attempts a recovery by pulling back on the elevator.

The airplane at this point doesn't have a habit of doing anything other than coming apart when the pilot executes an improper recovery from an extreme unusual attitude. The wing failing or the tail failing really makes no difference to the outcome of the event. The design limits of the aircraft were exceeded both by velocity and G loading.
Click to expand...
The point of my story about the tail failing first events was to point out that everyone worries about the wings coming off. They're focusing on a single parameter when there are multiple possibilities for failures.
Pinecone said:
Except the definition of Vno states is is the maximum in smooth air, but you can go over it if the air is smooth. :D
Click to expand...
Yup. That's because they're not at redline yet. Redline you don't exceed.
 
Kitch said:
The worst of it was definitely crossing the berkshires we started at 5500' which I suspected would be too low as it was a somewhat gusty day. 7500' was much smoother contemplated 9500' but by then we were almost to ORE and it was smoothing out a bit by the time we got to ORH it was no factor.

So the short answer to your question the first 1/3 of the trip was the worst and was still doable. None of the stuff on the floor ended up touching the ceiling, and no heads made impact with the ceiling either (like they did on my wifes 1st XC trip with me in a rental 172 LOL)
Click to expand...

It's a little longer, but I fly it going south from Glens Falls down the Hudson River valley, just east of the Albany class C, then turn east around Columbia County airport or so, to cross the Berkshires at about a 90 degree angle. Less transit time over the hills, way more landing options, and usually smoother. Plus it's just as scenic a trip. Once you cross over the ridge and are into Mass, it's pretty much flatter so *usually* smoother. Mostly, though, I go that way because it's less easy to get lost flying pilotage, and I'm a big baby in preferring overflight of farms vs hills.
 
Albany Tom said:
It's a little longer, but I fly it going south from Glens Falls down the Hudson River valley, just east of the Albany class C, then turn east around Columbia County airport or so, to cross the Berkshires at about a 90 degree angle. Less transit time over the hills, way more landing options, and usually smoother. Plus it's just as scenic a trip. Once you cross over the ridge and are into Mass, it's pretty much flatter so *usually* smoother. Mostly, though, I go that way because it's less easy to get lost flying pilotage, and I'm a big baby in preferring overflight of farms vs hills.
Click to expand...

I did consider a similar route before we launched, and most likely will do something like that in the future. Landing options are definitely limited for quite a while going direct.

Cue up all the people that fly around the rockies to bust my chops about our east coast "hiils" turbulence and landing options....:cool:
 
FC4571FB-1BB2-4BA0-8E64-2C9C4299E2D8.jpeg
kaiser said:
Depends on how severe and what model I'm in. Anything Piper I'm probably slowing early. Most any other make, I'm a few knots under yellow arc.


Some folks (myself included) use Va as an approximation of a rough air penetration speed. IIRC Cirrus has that as an actual speed.
Click to expand...

ouch!! ;-). Any Piper? Those flight school Pipers are plenty strong, but they take inhumane abuse flying low and in choppy air their whole lives, teaching students how to land 10 times an hour. Here is the wing spar on a Piper M600, machined from a solid piece of aluminum. You could stack several SUV’s on either side of that machined spar and lift them.
 
Rockymountain said:
View attachment 117351

ouch!! ;-). Any Piper? Those flight school Pipers are plenty strong, but they take inhumane abuse flying low and in choppy air their whole lives, teaching students how to land 10 times an hour. Here is the wing spar on a Piper M600, machined from a solid piece of aluminum. You could stack several SUV’s on either side of that machined spar and lift them.
Click to expand...
To be fair, I've so far been limited to only flying abused Pipers. I'd probably change my tune in the M600!!! :D
 
Dan Thomas said:
If I recall correctly, it was a left-right full rudder event. The fin is stressed in one direction, bending it somewhat, then it's suddenly thrown the other way, with more travel due to the first deflection. It fails.
Click to expand...

During the final input sequence, the initial full rudder deflection yawed the aircraft several degrees. When full opposite rudder was applied, the combination of load on the surface of the already yawed vertical stabilizer and the additional load on the stabilizer from the full rudder deflection (the loads were on the same side of the vertical fin and rudder) exceeded the structural limits of the vertical stabilizer/fuselage attachment lugs and they failed.

The opposite side of the vertical stabilizer and rudder did not experience positive loading during the failure sequence. The combination of same side yaw loading on the vertical fin and full rudder deflection was the cause of the crash.

While the A300 vertical stabilizer theoretically could have withstood the calculated loads from quick full rudder deflection in opposite directions, and that was the basis of the belief by American Airlines and its pilots it was OK to do so, making the immediate opposite control input did not consider the additional load already acting on the vertical stabilizer after the aircraft had been placed in a yawing moment.

Post-accident calculations confirmed the combined loads had exceeded the failure threshold of the attachment lugs.

I recall reading about the determination of the accident sequence by the NTSB in an AW&ST article not long after the crash. The Board had been working feverishly since the accident to discover the cause of the vertical stabilizer separation, and arrived at their conclusion in what must have been record time. The crash was extremely alarming, since the failure occurred just weeks after 9/11.

It took less than a minute to understand how the actions of the first officer had caused the stabilizer lugs to fail, and it was surprising to me. I had never considered that yaw coupled with rudder inputs placed loads on the assembly that could easily exceed design limits.
 
Last edited:
3393RP said:
During the final input sequence, the initial full rudder deflection yawed the aircraft several degrees. When full opposite rudder was applied, the combination of load on the surface of the already yawed vertical stabilizer and the additional load on the stabilizer from the full rudder deflection (the loads were on the same side of the vertical fin and rudder) exceeded the structural limits of the vertical stabilizer/fuselage attachment lugs and they failed.
Click to expand...

That is the similar situation with rolling G. The F-15 can pull 8 G, but if rolling, the limit is only 2.5 G.
 
3393RP said:
During the final input sequence, the initial full rudder deflection yawed the aircraft several degrees. When full opposite rudder was applied, the combination of load on the surface of the already yawed vertical stabilizer and the additional load on the stabilizer from the full rudder deflection (the loads were on the same side of the vertical fin and rudder) exceeded the structural limits of the vertical stabilizer/fuselage attachment lugs and they failed.
Click to expand...

Ah, thanks. Just one more example of unforeseen (or ignored) factors when designing the airplane.
 
Dan Thomas said:
Ah, thanks. Just one more example of unforeseen (or ignored) factors when designing the airplane.
Click to expand...
More appropriately misunderstood (or ignored) design criteria when flying the airplane.
…which sounds more critical of the pilots than I intended. One of the factors is that the part of the flight envelope that they were operating in required very little rudder pedal input to get those full deflections.
 
When my head slams into the roof I usually slump down, tighten my seat belt and slow down a little. Remember the maneuvering speed was configured at gross weight..if you are lighter than gross, the maneuvering speed is actually lower.
 
Rockymountain said:
View attachment 117351

ouch!! ;-). Any Piper? Those flight school Pipers are plenty strong, but they take inhumane abuse flying low and in choppy air their whole lives, teaching students how to land 10 times an hour. Here is the wing spar on a Piper M600, machined from a solid piece of aluminum. You could stack several SUV’s on either side of that machined spar and lift them.
Click to expand...

Neat photo. Whats your Va speed?
 
Gilbert Buettner said:
Help me out here. How does keeping your speed up change the crosswind component?
Click to expand...
I guess I misspoke here. Let me get another crack at it although it is hard to be succinct:

While it is clear that rudder effectiveness increases with greater speed and can help in the big crosswind, then if the crosswind component stays the same, the increased forward speed will result in the aircraft in a lesser crab but still in a crab with respect to the runway. When the crab is taken out and the sideslip is introduced, a side vector is created to counteract the crosswind component. The added rudder effectiveness is now used to torque the fuselage enough to allow the fuselage to fully allign with the runway.

Having said that, landing on a runway diagonal will decrease the crosswind component on the aircraft compared to a direct down the runway landing.
 
Last edited:
I have used the diagonal technique for crosswind takeoffs and landings for many years. I do understand control effectiveness at higher speeds, but there is no speed factor on the crosswind component chart. So I think the crosswind component stays the same, but you get more control authority at a higher speed.
 
Gilbert Buettner said:
I have used the diagonal technique for crosswind takeoffs and landings for many years. I do understand control effectiveness at higher speeds, but there is no speed factor on the crosswind component chart. So I think the crosswind component stays the same, but you get more control authority at a higher speed.
Click to expand...
Just to be clear, I’m agreeing with you. I only put the “if” in the statement above because, in my experience, the crosswind is often not constant because of gusts and varying wind directions.
 
You must log in or register to reply here.
Back
Top