I know you all have 100 times my hours......but...this is a common misconception... and is just NOT true..

the "myth of maneuvering speed" stems from everyones instructor telling them they can yank and bank below 110kts in there 172...

http://www.flyingmag.com/article.asp?section_id=12&article_id=527



its Boeing's policy that even in an upset situation.. (nose high\low\inverted\stalled\whatever) that flight crews keep there Feet OFF the rudder peddles! the moment arm is just too large for fighter jocks and 8kcab pilots to be slapping the rudder around.

it should only be used for crosswind landing and engine out situations ONLY. (or if all other methods to control prove unsuccessfully;) )

this is straight from David Carbaugh, chief pilot, flight operations safety, for Boeing Commercial Airplanes.

-nick

Air,

Interesting thing is having a conference right now. More interesting is those that are here.

The article disagrees with the definitional understanding from Pax river, Lockheed, an Airbus instructor and mine. As I stated the reversal my create other bad Bernoulli things to happen that then could lead to destruction but the certification definition is what it is. From what I gather from a 777 IP the feet off is the best policy for that acft with it’s FWB. Then again Airbus FWB logic and implementation is not thought of as nearly as highly as the early F/A-18 system which has an ejection seat to help mitigate it’s deficiencies.

I’ll go with what my and other professional pilots plus test pilots plus design engineers have a common understanding of the definition.

S/F, FOG

The FAA signed off on that didn't they? Another promised, but not fulfilled, security for the public.

I have one of those with a Harrier and an Apache too.

Lemme post em, they both kick butt:

The (ahem...ARMY!) dudes in the Apache film especially.....balls THIS big!

Harrier:

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APACHE:
<object width="425" height="350"><param name="movie" value="http://www.youtube.com/v/XZvWoK8mbqw"></param><param name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/XZvWoK8mbqw" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"></embed></object>

First time i ever rode in a private plane, about 12 years old, the pilot did a NOSE DIVE, unnanounced, out of nowhere(he was a real jokester his whole life).

Holy shiit it scared the living snot out of me!

Now I'm a bit confused...

The Boeing guy says don't use rudders unless XYZ which excludes countering turbulence at low level..and I would assume Airbus' advice is similar... so based on that the handling pilots' actions were ill advised at best...

And the Airbus apparently had known defects which would have caused the failure and should have prevented it from being operated commercially initially...

Does anyonelese think that somewhere along the line somebody allowed a plane with a known flaw to be operated in a manner inconsistent with the advice of reputable aircraft builders...

Now I know its not as simple as that but it really does beg the question...if the weaknesses were known and the flying techniques were also known (Im' making an assumption here that the advice from Airbus re rudder operations is not dissimilar to that from Boeing...) how did this airline manage to train its pilots to operate such an aircraft in such a manner? Its almost as if the knowledge from one source was not combined with the knowledge for another in order to create the full picture....very curious.

Joe...

604s are nice..don't have quite the same 'attitude' as a G550 tho'...but then nothing else really does....

MFAFF,

From what I understand the known flaw in that particular composite block was thought to not be important and sent up the Airbus chain.

You have to be careful on what the Boeing chief pilot is being quoted. The 777 supposedly has a well thought out and executed FWB. Other Boeing’s are different. I talked to some of the heavy instructors (both people and freight haulers) and the consensus is that they get a lot of fighter/attack types trained by the USAF, i.e. not well trained in rudders and let the acft try and fly itself out. Using all the flight controls plus differential power is also taught in more than a few places both commercial and military.

Airbus advice is based on weakness in the vertical stab system plus a heavy reliance on their FWB system. I have zero experience with their FWB system know pilots that have experience with others and according to them the Airbus is to be polite severely lacking.

S/F, FOG

FOG,

Interesting on that composite block...so who knew? Was it at certification? Either Eurpoean or US?

The aspect that really catches me is the knowledge of weakness being deemed acceptable yet the training not being aligned with that knowledge.

That the A300 FBW is not as good as the 777 is unsurprising as its several generations older..in fact it could be regarded as only the second ever FWB installation in a civil airliner and the first in a mass market one (#1 being in Concorde, hardly a mass market bird) whilst the 777 is significantly younger and one would hope better.

Agreed that training philosophies may well be very different but would be surprised if the manufacturers' advice on the role of a rudder on a conceptually, phyiscally and control-wise similar bird would vay greatly.. afterall the phyiscal demands on a 777/ A330 are broadly similar due to size rather than than the requirements of their FBW systems...

From second hand stories and experience I think the Airbus FBW system is far more 'intrusive' than the Boeing one....and allows the pilot far less freedom of action....different appraoches I guess which may reflect the different experiences of the 'majotiy' of the native pilots....

Hey guys, the video of the crash....did the plane lose all lift due too the extreme angle of the wings? looked like it just fell out of the sky.

I may be wrong on this (I don't think so, however), but I do not believe that Airbus ever cautioned any operator against rapidly deflecting the rudder to full deflection in one direction followed by full deflection in the opposite direction in the A-300. As some or all of you may know, the A-300 is not a FBW aircraft, so the flight and upset recovery techniques used in the later Airbus FBW aircraft (A-318, 319, 320, 321, 330, 340, 380) would not apply to it. The admonition against this type of rapid, cyclic rudder deflection only came to light after the accident, when Airbus asserted that certification standards did not require the aircraft to be able to withstand this sort of action. Interestingly enough to me, I believe that the authorities had to conclude that Airbus was, in fact, correct with their assertion.

Up until the accident, I had never heard of this type of failure mode in a certified aircraft that was flying below Va. I know of no pilot that knew of this type of weakness in an aircraft. Pilots have always been taught (yes, even "Flying" Magazine's J. Mac McClellan) that flight at or below Va in any aircraft would prevent structural failure. The airplane would simply not be able to generate the aerodynamic force necessary to cause damage before an aerodynamic "stall" would occur. Flight through severe or worse turbulence, of course, would alter that rule a bit, due to the very rapid and uncontrollable changes in airspeed possible in this type of turbulence.

At my airline, airspeed limits have always been given in the "limitations" section of our Aircraft Operators Manual (AOM), along with the admonishment not to use full control deflections above the Va speed. That was it. Now, however, our manual states (as does every operator's, I believe) additionally that full and rapid rudder deflections, first in one direction, and then the other are to be avoided at all speeds, even those well below Va due to the possibility of structural failure.

As far as I know, this is not something anyone at AA (or any operator of the A-300) knew about before the accident. I believe this is something everyone discovered afterward - that no aircraft is technically required to be able to withstand this kind of back and forth rapid deflection of the rudder.

This is what I am aware of, btw. I do not claim to be the expert here. I am simply someone who is a pilot in this industry with a genuine professional interest in it (for 15+ years).

I understand you may not agree with the entire link .... but if your understanding of the definition is that below Va offers structural immunity in every situation then from what i know you were misinformed. I'm sure i just misunderstood you.


The Boeing guy i quoted earlier is my father. From what i gathered from the dinner table(so dont quote me on this) it was a combination of many factors. American Airlines did have alot of USAF types. The people in charge of training were also "heavy on the rudder" types. Also when they taught upset training they disabled the use of the ailerons until in 60 degress of bank for some situations. so the pilots quickly learned to use the rudder more often then necessary. That combined with the fact that requiring full deflection in both ways rapidly when calculating Va is not required for normal category aircraft, something most pilots don't know. The tail is WAY far back there... and the forces\moments it can produce at full deflection are pretty high... there just wasn't enough education on the subject because no-one has ever heard of this kind of incident before the AA crash.

or at least thats what i remember.


very True. Thats why the misconception about the immunity below Va needs to be explained to everyone with a yoke or a stick in there hand. "moving the rudder from stop to stop is not a required certification load limit in normal category airplanes"

below Va = accelerated stall before over-g only in pitch..............Most of the time.........


-Nick (a sub 300 hour whippersnapper):p

This is what I am aware of. I do not claim to be the expert here. im not trying to make anyone angry. I am simply someone who had to listen to this crap at the dinner table..

Air,

My background is a Marine and therefore Naval aviator. I am currently active duty with the reserves in Ft. Worth and we have instructors from AA, United, FedEx and a couple of others. We also have reserves that fly as civilian pilots at Pax River. A couple of former Marines that have worked for me now work on the other side of the runway (JSF and F-22).

Our understanding is that below maneuvering you should not have failure due to control movement. That is not to say that you couldn’t get yourself into another area that would have consequences.

The USAF types and rudders is experience. Having nuggets come through the USAF system, exchange IPs, and talking to heavy commercial instructors the USAF are far behind the Naval types in use of rudders. I am sure that most who have been around for a while can get a good idea of what a pilot’s background is. Each community is different. Even in naval aviation you will find F/A-18 differences between A-C and D and USMC vice USN training. We’re getting off topic discussing the pros and cons (I’m a believer that USN should still be paying more attention to blue water issues, USAF the deeper strike, and USMC CAS with each being able to help out in each other arena vice what is happening) as an example.

450,

I’m strictly military but from my understanding that this could happen was known by Airbus but not forwarded for ??? reasons. Add in that a particular composite part for this acft had issues and then installed…

Pulled a KC-130 NATOPS and it has a warning about not going full reversal in certain conditions to possibility of rudder fin stall which could lead to other bad things.

MFAFF,

The Airbus predates the 777 but not the early F/A-18. Those that have dealt with both are emphatic that the Airbus is lacking and doesn’t have an ejection seat. I will give that the Airbus generally are more comfortable and quieter from a passenger POV.

S/F, FOG

Guys,

Very interesting responses...thanks its a pleasure.

FOG...

Looking quickly over some dates the A300 programme predates the F/A 18 programme...being more contempary to the YF-17.....remember the Airbus took even longer to appear as a product.

But that's beside the point...I would however grant the systems are not nearly as 'able' as those of a highly agile multi-role aircraft...and they certainly don't have ejection seats.

On a wider issue I'm interestes in the apparent difference in flying 'philosophy' between close communities...especially the A/B: C/D 18 communities..I do not know the differences in sufficient detail between the versions but from the outside it is difficult to see why such differences exist....more interesting still is USMC/USN differences in flying the same type of a/c...is not the basic training common and all specialist training to the same standard? Again forgive my ignorance.

Air,
Very interesting....thanks..


To me this thread is one of the prime reasons why this board is so good..

The equation for maneuvering speed according to the book "Aerodynamics for Naval Aviators" on page 339.

is Vp = Va (square root) n-limit

Vp = maneuver speed
Va= stall speed
n-limit= limit load factor

another way to find it would be the point were a the stall line crosses above the load limit factor in a Vn diagram. also there is a safety factor added in because a gust load may be encountered why at this speed.

http://members.aol.com/milleratad/images/v-n.jpg

So the Va is biased on load factor.


"The flight load factor is defined by the proportion between airplane lift and weight where:

n= L/W

n=load factor
L=lift, lbs
W= weight, lbs"


so 10,000lb aircraft with 20,000lbs of lift would be 2 "G's" or a load factor of 2.

you cant change weight on the fly... but how you increase lift is increasing the airfoils Angle of Attack. And how you do that is with the elevator.

Va is only a number that involves exceeding the limits in pitch. Not rudder... so as i understand the AA flight didn't exceed the limits in pitch.. and was below Va... but still over "G'ed" the structural limit of the vertical stabilizer by swinging the rudder back and forth violently a few times.

You may never be able to exceed the structural limits of any of your controls on a fighter aircraft below Va but on other aircraft... such as a really big transport category aircraft...... the speed of Va is only a guideline for pitch and is not guaranteeing ANY limits of any OTHER control surface..


I'm not trying to be a jerk here...or to beat you up over this or anything... but this is something that could kill you and anyone flying with you. Anything beyond this explanation is is starting to get over my head and i would be happy to refer you to someone who could talk to you on a more technical level or who is carrying more credentials then i have so far obtained..

-Nick

Air,

I have a passing familiarity with aero for nasal radiators and the equations.

We’re talking different things. What are the standards? As an example the turbulent airspeed for a KC-130 (since I have access to both NATOPS and performance manuals) is below Vp. Part of the certification standards for .mil acft as explained includes full control movement with reversal at or below Vp. If the acft doesn’t meet the standard then either fix it or address it appropriate notes, warnings, and cautions. I may be wrong on the acceptance/testing standards but I have some familiarity with accepting a couple of fixed wing acft. If you want to talk to rotary or Osprey then I’m not well versed.

It is interesting what the FMF and fleet aviators figure out by studying the performance manuals added to knowledge and experience. Wonder how the unrecoverable (as defined by the manufacturer and TPS) F/A-18 became recoverable? Fleet aviators went out and safely did it repeatedly then they instrumented it. KC-130 take off and landing data is still as specified and use the numbers for the nuggets. I can go on.

Part of the reason that the above happens is the test folks have to go with parameters that are specified by someone else. Service and cruise ceilings along with max endurance numbers are defined with flaps up though the fleet beats these numbers by the simple expedient of dropping flaps to 10-12 percent and reducing overall drag.

Back to the AA example. The other transport that warns about full rubber reversals is the C-130 series. The warning has to rudder fin stall that can lead to other very bad things if not properly recovered from. As stated here and talking to a couple of Airbus instructors the admonishment is only after the mishap and no one will answer the question they have on certification.

I don’t take you as being a jerk but as ill informed civilian aviator who views the military the publicly presented knuckle dragging neanderthal who may have been a NASA engineer advanced degrees in various “hard” disciplines” etc. combined with real world experience.

S/F, FOG

MFAFF,

The A-C communities are single seat while the D is a two seater having someone with No Future Outside in back. The D is a better platform for FAC A, etc. The airplanes specifics lead to different philosophies. USMC-USN. The USMC is more concerned with Blue then into brown water then CAS. USMC obviously more CAS centric.

Add in the USAF differences in philosophy and you see clear differentiation when get to know the types.

I think these differences are a good thing. The various services and communities concentrating in specific areas with a broad knowledge of other areas. Then when needed going to Subject Matter Experts to help out.

This subject has been gone over at length and in detail by the various service personnel with the help of appropriate applications of libations.

S/F, FOG

Since that is certainly not the case, we must be talking about different things
T
The certification standards for military aircraft is something i know nothing about. I thought we were talking about large jet transports in relation to the use of the rudder below Maneuvering speed.

particularity your phrase:

"The definition of maneuvering when used to certify for FAA use means that no structural failure will occur with full deflection back and forth on the rudder."

the certification standards for transport category's aircraft
per 14 CFR part 35 subpart C in reference to 25.351 say pretaining to " Yaw maneuver conditions."

The airplane must be designed for loads resulting from the yaw maneuver conditions specified in paragraphs (a) through (d) of this section at speeds from VMC to VD. Unbalanced aerodynamic moments about the center of gravity must be reacted in a rational or conservative manner considering the airplane inertia forces. In computing the tail loads the yawing velocity may be assumed to be zero.

(a) With the airplane in unaccelerated flight at zero yaw, it is assumed that the cockpit rudder control is suddenly displaced to achieve the resulting rudder deflection, as limited by:

(1) The control system on control surface stops; or

(2) A limit pilot force of 300 pounds from VMC to VA and 200 pounds from VC/MC to VD/MD, with a linear variation between VA and VC/MC.

(b) With the cockpit rudder control deflected so as always to maintain the maximum rudder deflection available within the limitations specified in paragraph (a) of this section, it is assumed that the airplane yaws to the overswing sideslip angle.

(c) With the airplane yawed to the static equilibrium sideslip angle, it is assumed that the cockpit rudder control is held so as to achieve the maximum rudder deflection available within the limitations specified in paragraph (a) of this section.

(d) With the airplane yawed to the static equilibrium sideslip angle of paragraph (c) of this section, it is assumed that the cockpit rudder control is suddenly returned to neutral.

[Amdt. 25–91, 62 FR 40704, July 29, 1997]



In other words.. what is required concerning yaw at Va is only full deflection in ONE way from "unaccelerated flight at zero yaw" and then stabilized in that condition. Also from a stabilized side slip with full deflection the control input is released.. no "back and forth" or "you can slam the controls around any way you like"


For more information the NTSB has a site dedicated to flight 587 with plenty of info.

as to how this Reg applys to ripping off the vertical stabilizer below Va? you can refer to page 2 of there reccomendations:
http://www.ntsb.gov/Recs/letters/2002/A02_01_02.pdf

I may not have any advanced degrees in various “hard” disciplines” but ill informed i am not.
-Nick

FOG,

Thanks.. I know the D is a two seater.. but its aero config is the same as the B, much in the same way as an A is similar to a C....so differneces between A and B are understandable..but A to C or B to D are not as clear...

That the EFG models are yet again different is not surprising as they are different aircraft to the A to D versions...

Its the differences in the A and C communities that you appeared to allude to that interested me.. perhaps I misread.

Air,

The single reversal aspect is crucial here.....if certification is based on this..and it would appear to be the case...then how is an operator to define the proper methods of operation WRT to this aspect...
If the aircraft has demonstrated that..but nothing more is the operator to assume that it not able to carry out more than one deflection or are they to assume it can but that this may result in damage...

It seems as if there was a gap in the overall knowledge of what the aircraft was able to do in this instance and the price of finding out was rather high....

yes a huge gap as to what the FAA requires and what is taught.

More importantly, what the FAA requires vs. what it SHOULD require for certification.