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VGCM66
Thank you sir. In your link, we read an opinion from BEA as to what the crew "concluded". On its face, this statement is preposterous, since it imputes conclusions to the pilots based only on comment they made earlier. No one in public knows what the pilots were thinking, and BEA, having tipped their hand, may know, and appear to be rigging the playing field. BEA present it as fact. This release contains condemnation of Airbus and the airline sufficient to confirm my proposal. Read it with care, allow for some interpretive changes, and the accident falls to Airbus almost completely. This fatal wreck happened in the ten seconds post a/p loss, and the pilots, though involved, were not entirely responsible. One needs to take the BEA with generous portions of salt. What about "Rapid Climb", and "the aircraft was not immediately responsive" sounds familiar? Think of another similar incident, one with a better outcome. @Machinbird. Your cite of PIO is instructive. You neglect another form of out of sync C/R. Autoflight induced oscillation. AIO. |
I have a long flight ahead of me today.
I'll be back. |
Originally Posted by Lyman
@Machinbird. Your cite of PIO is instructive. You neglect another form of out of sync C/R.
Autoflight induced oscillation. AIO Judging from where the Autoflight system dropped the aircraft (essentially on altitude, essentially on speed, essentially level) and the fact that the Autoflight system dropped completely out at the cavalry charge, your comment would seem to have no merit. Oscillations generally have a characteristic frequency. What characteristic frequency do you suggest for this phenomena? |
Lyman, you're going so far off the deep end by coming up with these ever more elaborate excuses as to how it must have been the aircraft's fault that you have now officially transited the boundaries of known space into la-la land as far as I'm concerned.
You're trying to parlay the autoflight's interrupted response to a comparatively large bump from turbulence - of which not one cycle was completed before the PF took control - into a hitherto-unknown phenomenon that you've just invented. I mean, extrapolation is one thing - but what you're suggesting has not only never been known in the hundreds of thousands of hours the type has been in service, but completely contradicts the evidence at hand. |
Lyman,
You repeatedly attribute statements to BEA that I'm unable to find in BEA's publications: "The aircraft did not immediately respond..." BEA One needs to take the BEA with generous portions of salt. What about "Rapid Climb", and "the aircraft was not immediately responsive" sounds familiar? |
Originally Posted by Lyman
Autoflight induced oscillation. AIO
Thanks for confirming, once more, your total ignorance of basic aircraft stabiliy, and automatic flight control system design and testing. |
Quotes supposedly from BEA
I am also curious where those quotes come from. A word search of the BEA reports and press releases reveals no such quotes contained in any of them.
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Machinbird
Whilst I do not doubt the phenomenon exists I was reading your post as an indication that you believed the design of the sidestick played a part for inducing the oscillations. This is what I was questioning. All evidence from the Airbuses flying is that the sidestick is a reliable and useful input device with very little in the way of vices. The more I see of the evidence the less it appears that the machine had any role in the accident. There is no 'smoking gun' as it were; just pilots who were not adequately trained or prepared for what should have been a recoverable situation. |
Originally Posted by OC
Machinbird
Whilst I do not doubt the phenomenon exists I was reading your post as an indication that you believed the design of the sidestick played a part for inducing the oscillations. This is what I was questioning. All evidence from the Airbuses flying is that the sidestick is a reliable and useful input device with very little in the way of vices. The more I see of the evidence the less it appears that the machine had any role in the accident. There is no 'smoking gun' as it were; just pilots who were not adequately trained or prepared for what should have been a recoverable situation. [theory] The AF447 PF made too large of an initial lateral control input and ended up sending the aircraft into a roll oscillation which can be seen in in the BEA charts. He attempted to 'get ahead' of this oscillation by making even more rapid control deflections, but ended up continuing to drive the oscillation. In his frantic attempt to move the stick even more rapidly against the drag of the roll viscous damper, he brought the canted forward stick back from neutral into the nose up direction to obtain better mechanical advantage (since the stick being vertical gives him a greater lever arm). This response would be automatic if he was concentrating on his roll control problem. [/theory] I agree that the sidestick can be an accurate, useful, and safe means of control. However, the A320 does have occasional problems with roll PIO. Perhaps the A330 does as well in the correct circumstances-like in roll direct mode at altitude. When a pilot encounters PIO, one of the natural reactions is to believe that the control system is malfunctioning. Most of us would find this extremely disconcerting. It would be good for a double dose of adrenalin.:eek: An experienced pilot would change his control strategy to break the oscillation. An inexperienced pilot would likely continue the oscillation until he tired of the effort of driving it. That is what the BEA charts seem to indicate. (And as the roll oscillation began to get under control, so did the nose attitude.) PIO is a complex condition and should not be blamed on just the sidestick design. If roll PIO was a player in this accident, then the fixes are relatively simple. Roll direct is an infrequent operational mode. Roll direct at altitude will be even scarcer. It is entirely possible that only a small percentage of pilots employ "high gain" control strategies that would trigger a roll PIO. BTW the C-17 aircraft was very late in its development cycle before its roll PIO characteristic was identified and corrected. Training to avoid "high gain" control strategies would help pilots avoid PIO. Perhaps we need a PIO training device to teach pilots how to avoid it.:} Meanwhile, "mayonnaise stirring" should definitely be avoided on Airbus type aircraft. |
Machinbird
I see what you're driving at now and as a mechanical explanation of the exact process it certainly has merits. However, I suspect that the reaction of the PF would have manifested itself in a similar manner no matter what the input mode. This was not a pilot who was thinking clearly or logically and this was not a crew that was following any known procedure. The proper management of the flight deck was missing and whilst I like the mechanical process you lay out I don't see it as having anything to do with the development of the accident other than the in the most peripheral way. A330 pilots who have commented on the flight characteristics of the aircraft on these threads indicate that the aircraft is a very stable machine which quickly recovers a stable flight regime even in ALT2. The aircraft seems to be designed to help the pilot as long as the pilot trusts the aircraft. |
A330 pilots who have commented on the flight characteristics of the aircraft on these threads indicate that the aircraft is a very stable machine which quickly recovers a stable flight regime even in ALT2. The aircraft seems to be designed to help the pilot as long as the pilot trusts the aircraft. Machinbird's point on "control strategy" strikes me as well made. His theme takes us back to currency, familiarity, and training in the modes of hand flying a pilot may be exposed to. |
For what it may be worth, and I have no illusions, imho, Machinbird is spot on. BEA, having assembled an "HF" group, is attempting to shepherd Opinion in the direction of events that came after the initial blunders, and the aircraft's shortcomings. With a focus on the initial ten seconds and the initial climb, comes widening culpability for the airframer.
BEA quotes: Keep looking, and in their discovery, one may get a picture of how BEA is manipulating the facts. "ICE, NOT ICE". @Alpha Zulu Romeo. On the contrary, the ICE issue is perhaps the single most important factor in the solution of this mystery. "ICE", if proven, deflects focus away from the airframe's inabilities to deal with loss of Speeds. If "NOT ICE", we need to look at AIRBUS' blunders in providing a straightforward solution to Autopilot/Pilot transition, rather than an after the fact publication of accidental and in service mitigations and recoveries. All the defense on this thread of how simples it is to recover an a/c from uncued maneuvering and loss of indications will not hide the fact that there are some obvious and systemic problems with this aircraft. There is a reason the a/p is disconnected prior to landing, and hazards of airmass therefrom. Generally, the a/p should be disconnected when entering turbulence as well. Better to not let the a/c try to solve something it cannot fix. |
Originally Posted by Lyman
(Post 6902278)
Generally, the a/p should be disconnected when entering turbulence as well.
Better to not let the a/c try to solve something it cannot fix. We got that sorted on Concorde about forty years ago.... http://www.concordesst.com/inside/co...tures/ap13.jpg |
@CJ :
No point wasting your breath (or fingers), he's long since stopped taking any notice of anyone saying anything that does not fit his theory, and cherry-picking bits from other posts that he can somehow twist and work in there. His argument seems to be that there's a massive cover-up going on - to whit, the BEA are steering the outcome to "pilot error" because they aren't taking into account the shortcomings of the aircraft based on a bunch of things he just made up. (Not to mention ignoring facts like the existence of autoland since the '60s...) There's no "TURB" switch on the Airbus FBW series autopilot as far as I'm aware, but the established procedure seems to be to engage the "Mach/Speed" mode when encountering turbulence, as it monitors airspeed much more strictly - discussed here: http://www.pprune.org/tech-log/46809...ence-a320.html Of course that's not particularly relevant to this case as they had no speed data and thus no A/THR, and even beforehand the thrust remained fairly stable. |
DW, I too have long-ago lost patience with Lyman's fantasies (quit reading them) BUT!: :uhoh:
I too believe that BEA will make sure that the pilots are blamed. France cannot afford any other outcome. ("Billions and billions.") There is plenty of evidence, though somewhat subject to argument (of course) that there are interface problems with the design, as well as the well-known pitot problem. |
Gents. From Organfreak, I am reminded of an expression that might apply.
Try not to throw the baby out with the bathwater. BEA have been responsible in the past for rigging the results, and utilizing phony data. For a great deal less than the very existence of AIRBUS, and with it perhaps the economy of FRANCE. If this turns out to be another "Uncommanded climb", Airbus doesn't have franc one to cover the liability. Let alone the criminal exposure. Someone ran risk/benefit and figured it was worth the exposure. BEA have shown all manner of unprofessional conduct, flaws in the reporting of their data, and parochial "Memoranda" for mere Market share purpose. I realize it is difficult to entertain such an accusation, but I believe the truth will out, here, and I believe the Pilots will be exonerated. Just as you believe your defense of the system is worthy, so do I my challenge of it. I harbor no ill will, and as you will note, I continue to refrain from personal attack. For the simple and exclusionary reason that My respect and admiration for you all runs pretty deep. It does not occur to me to attack, except those I believe are culpable for the tragedy. |
Turbulence dampening mode
DW There's no "TURB" switch on the Airbus FBW series autopilot as far as I'm aware, but the established procedure seems to be to engage the "Mach/Speed" mode when encountering turbulence, as it monitors airspeed much more strictly - discussed here: LHTTM TURBULENCE DAMPING FUNCTION (bolding by me) General The purpose of the Turbulence Damping Function implemented in the Electrical Flight Control System is to damp the structural modes induced by atmospheric turbulence. Architecture The Turbulence Damping Function consists of two lanes: Longitudinal lane The longitudinal Turbulence Damping command is computed by the FCPC1 (FCPC2 as a redundancy) as a function of the Nz accelerometer information. It is added to the normal law command and transmitted to the associated elevator servo-controls. Rear lateral lane The rear lateral Turbulence Damping command is computed by the FCPC1 (FCPC3 as a redundancy) as a function of the informationof a specific Ny accelerometer located at the rear bulkhead level. It is added to the normal law command and transmitted to the associated yaw damper. Specific equipment The equipment specific to the Turbulence Damping Function are: - the TURB. DAMP pushbutton switch - the Ny front accelerometer - the Ny rear accelerometer. system knowledge........? franzl |
Back To Reality
Lyman
Your Quote: Generally, the a/p should be disconnected when entering turbulence as well. Better to not let the a/c try to solve something it cannot fix. It is getting more bizarre with every post. Here are two quotes that make much sense to me: 1. From Takata Events Leading To LOC (my words) Illusion, deceleration, and weather. - Illusion because altitude recorded is "indicated", then partially false at UAS point. - Deceleration, because autothrust started to reduce N1 by 16% seven seconds before UAS event. - Weather because there was an up/down/up. All they needed to do was to: 1. Take a deep breath and watch what the aircraft did under the pitch and power that was set before the AP dropped out. 2. Make gentle corrections to ensure that altitude and heading were maintained within some reasonable limits given the turbulence encountered. Further, Why did they get to where they got to when all this happened (A/P disconnect, A/T disconnect, etc.)? Why did they think the ITCZ was somewhere off in the distance and may have been surprised to find themselves in the middle of it? What were the cockpit conversations, P/F P/NF, not just 5 or 10 minutes before A/P disconnect, but 30 minutes before? Who was monitoring the weather radar? Was it being monitored? Was it set properly? IMHO, this is where the setup to disaster began, but not much has been said about this. TD |
TurbineD
With utmost respect, take a breath and consider how well both takata and Smilin Ed fold in with my projection of UPSET prior to UAS. A/T was reducing N1 due a severe Updraft, and combined it with a NOSE DOWN input additive. (takata/BEA) And the a/c lost 380 feet. ACARS shows a WINDSHEAR event early on, along with TCAS warn due exit of altitude approved. Ed is a bit more complex, since the a/c ostensibly, with Inertial recovered data, showed a PITCH resting on 0, (Three degrees+ LOW), and power that was set correctly for an airmass that was markedly different in two seconds from what was indicated and what he felt. In short, the system was dynamic, the AoA was nine degrees delta PITCH, and power was at ~73? STALLSTALL. Sound familiar? This behaviour was patent on other 330's and at least one 340 prior to 447. One cannot with confidence refuse to review patent behaviour in this accident. BEA would have it, and as you know, I trust BEA to be true to BEA past performance. The past will repeat, especially when there is no incentive to alter the march of the chariots. The aircraft is a long and heavy tube. Which accelerometer was which, again? |
The Turbulence Damping Function is part of the Flight Control System and not the Auto Flight System. It is normally on and not dependant on an AP being engaged.
There is no autopilot turbulence mode and the Turbulence Damping Function is somewhat different from the TURB autopilot mode of previous non-FBW Airbus. That would disengage pitch mode which would revert to pitch hold while the lateral mode would be retained and THS trim speed reduced. |
Lyman,
No, N1 was reduced for turbulence penetration by one of the pilots in anticipation of turbulence ahead. I asked PJ2 the question about how this is actually done, moving the throttle levers or another way. It was a pilot initiated action to slightly slow down. IMO, the A/P was doing what it does, making corrections for ups and downs. At the point of disconnect, it was correcting for an up and therefore the nose was down. From there on, what took place was pilot input. There was nothing wrong with the aircraft or its systems. The reason the A/P disconnected was UAS due to pitot icing, not turbulence. There is no evidence to support the "severe" turbulence theory, but plenty of evidence to support the pitot icing. In fact, I think that will be the #1 issue Airbus will address going forward. I think you will see some technological advances, perhaps on the A320Neo or even the A-350 if the program slips more. |
PF made a slight retard to .80 mach. AIR, that was it from the pilots.
How did the a/c get sideways enough to award a STALLSTALL to PF upon his first stick? His first input was nowhere near "full aft stick" which has become the Urban Myth collective bleat. ACARS, WINDSHEAR? TCAS? There is leeways aplenty for any analysis of the Turb value that the investigator wants. The noise heard by the pilots was not RAIN, nor was it ICE CRYSTALS, or Hail. I think it was a hellish updraft of perhaps 10000fpm, sufficient to start the entire a/c UP at 500fpm in 1.5 seconds. It's on the graph. The aerodynamic noise of an airmass turnaround/shift of 70-90 degrees is......noisy. I think the a/c was on the verge of a Stall, and dropped to ALTERNATE to sustain the NORMALLAWSTALLIMPOSSIBLE meme. notquite, but you get my drift? |
Originally Posted by Organfreak
(Post 6902728)
I too believe that BEA will make sure that the pilots are blamed. France cannot afford any other outcome. ("Billions and billions.")
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Originally Posted by Lyman
...PITCH resting on 0, (Three degrees+ LOW)...
Interim Report #3 page 86 states : Standard altitude (ft) 34.992 Computed airspeed (kt) / Mach 275 / 0.80 Pitch attitude (°) 2.8 Total weight (tonnes) / Centre of gravity (%MAC) 218 / 27.5 We can see that at the same altitude and speed but 13 tonnes heavier a pitch of 2.8° was required. At the actual weight of 205 tonnes the pitch would therefor have been less. Somewhere between 2 and 2.5°, probably closer to the 2.5 than 2. ...and power that was set correctly for an airmass that was markedly different in two seconds from what was indicated... Interim Report #3 page 88 states: 2 h 09 min 58 Speed handling changes from managed to selected. The selected Mach is 0.8. 2 h 10 Pitch attitude decreases from 1.8° to 0° in 3 seconds. In 8 seconds, the N1 commanded and the N1 change from 100 % to 84 %. A reduction in speed from .82 to .80 was selected and the ATS responded accordingly.
Originally Posted by Lyman
AoA was nine degrees delta PITCH
AOA did not reach 9° until approx. 02:10:55, some 50 seconds after AP disconnect and with the aircraft at 37500 ft. It did not exceed 6° untill 02:10:50, some 45 seconds after AP disconnect. See pages 42 and 106 of Interim Report #3. I am also still looking for references to where those quotes you attributed to BEA comes from. I don't think a "keep looking" will do. |
I will take a break, try to find my reference, and return. The "a/c did not immediately climb.." was in reference to the PF's first aft stick, airecall. So it would be post box dump, first analysis, afaik.
It was as BEA first analysed the beginning of the fatal climb. |
BEA have actually done a fine job and having found the FDR and CVR have identified the causes of the accident. This happens to be the flight crew sad to say. Attempts to involved the machine are just grasping at straws and filleting our shoals of red herrings. I like some of the mechanical explanations of the processes but these are not causal factors. Causal factors are lack of CRM, poor training (especially at altitude - as Lonewolf50 and Machinbird have ably identified), company culture, failure to follow SOPs, poor cockpit discipline, no designated pilot in charge when the captain left the flight deck, need I go on. The Air France safety audit which was linked a couple of threads back should be essential reading for everyone wishing to comment. It provides all one needs to know about the causal factors in this accident. BEA are attributing responsibility to the flight crew because that is where the responsibility is. The causal factors are all human factors NOT machine factors. Even the UAS was curable by waiting and following proper procedures. These were not followed and disaster was the result.
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I'm mostly wit Old Carthusian here
If it walks like a duck, talks like duck etc etc; then it probably is a duck.
Having said all that - I flew the A320 in the LH seat for just 2 years. Whilst a brilliant aircraft in many ways I can see how the inexperienced, and perhaps badly trained pilot, could be suckered into this type of event. It's still a duck though however you wrap it up. |
Lyman,
From BEA Interim Report #e3, p.89: 2 h 10 min 10: The stall warning is triggered. The angles of attack 1, 2, and 3 values are respectively 2.1°, 4.9° and 5.3°. 02 h 10 min 10,4 : SV : “Stall, stall” (without cricket) The stall warning threshold at Mach=0.8 has been documented prior to FDR recovery in BEA Interim Report no.2 and in the Air Caraibes memo to be slightly above 4°. Why is it so difficult to understand that the stall warning was triggered when the AoA exceeded the warning threshold due to the combination of sidestick input and a minor gust? |
Originally Posted by Lyman
(Post 6903177)
I will take a break, try to find my reference, and return. The "a/c did not immediately climb.." was in reference to the PF's first aft stick, airecall. So it would be post box dump, first analysis, afaik.
It was as BEA first analysed the beginning of the fatal climb. BEA went to great lengths to release (unprecedented, I think) public video of the search and recovery, including shots of serial numbers on the sea floor, recovery and storage with police/judicial oversight and multiple observers etc. I think it is extremely unlikely the flight recorder data is faked, and certianly can't be subject to the same allegations as Asseline made. The data clearly shows commanded climb, and the simulation with the same commands results in the same crash (without turbulence input). Aside from the loss of airspeed, that particular plane didn't fail on the night, and the crash was down to the pilot input. Whether or not there are design flaws that contributed to that pilot input is a different and more complex question. |
In the Rumours-News forum GerardC refers to NTSB Report DCA09IA064 which describes A330 UAS incidents to NWA and TAM. Interesting reading, in particular the TAM incident where the crew reengaged the AP when two airspeeds agreed but were still low.
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Remember that, in ALT2, the A/P physically cannot be re-engaged.
(ALT1 it can) |
HN39,
Thanks for posting the link to the NTSB report, just downloaded it into the 'archive' and read it. |
"Les cow-boy d'Airbus" is the title of Bernard Ziegler's book... HIMSELF ! :\
preface from Jean Pierson, Edition : Privat (TOULOUSE-France). This book has been written before the RIO-PAR crash... "The aircraft cannot stall", aso. :suspect: |
It is not just the Airbus.................
It is interesting to read this, especially the last block 'Who is to blame'
The moment a computer crash nearly caused my car crash ? The Register |
Big Red Button
Another reason to have a "BIG RED BUTTON".
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Another reason to have a "BIG RED BUTTON". |
There is no stopping people being stupid, except by selection and training to the extent possible.
The referenced report is a confession by a car driver that he almost got killed on a level crossing when his car was “acting up” – periodically slowing or stopping when supposed to be driving at a normal speed. So what did he do, when it was doing this and he approached a level crossing? “ . . .I decided to plough on forward and try to make it the last 20 blocks to the dealership”. Car drivers are not specially selected, and their (OK, our – including my) training did not and does not include much on fault analysis, nor on decision making. In aviation, there is selection, and training. But others, professionals, are pointing out that modern training is not covering enough of the old essentials that used to be acquired. Years ago, I was giving evidence to a UK House of Commons Select Committee about some aviation issues, and I pointed out that, too often, airlines only adopted safety measures if forced to by legislation, or if somebody else paid for it. I quoted as examples rear facing seats and the fatal accident at Manchester (?) where passengers survived the initial crash only to be killed by smoke inhalation – the airlines would not adopt measures to provide safe exit in the event of fire. Have they now? You know the answer. Do you care? Have you tried to influence any such decisions? Now, re AF447, many professionals are complaining about economising on training, late replacement of Thales pitots, and some mention not going for optional extra instruments or systems (AI, BUSS IIRC), etc.. I hope those who see deficiencies are raising these issues in their companies, and rousing BALPA etc., and writing to their governments. I should not have been alone, and from GA rather than professional aviation, in my representations to that select committee. IMHO. |
Sadly for those who would like to believe so we have no evidence that the accident was caused by anything other than pilot actions. Furthermore, this evidence is not likely to be faked or incomplete. What we do have is serious deficiencies in airline procedures and piloting skills which may or may not extend to other carriers besides Air France. There is some anecdotal evidence that training and piloting skills have been neglected outside Air France as well. However, this is an cultural issue not a complexity issue. It is possible to encourage a culture of excellence and professionalism and to reward this. Certain airlines fail to do this and Air France are just the latest example.
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AirBus should be Russian, Here the plane flys you.
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New Background Information on PIO
Recently I theorized that AF447 suffered a roll PIO condition that completely overload PF's ability to control other axes of the aircraft.
While looking for a definition of PIO to compare against the BEA data, I came across a relatively recent paper showing how thinking is moving on the subject of PIO. You can read the paper here. Aircraft and Rotorcraft Pilot Couplings – Tools and Techniques for Alleviation and Detection (ARISTOTEL) Among the key points in the paper are: An aircraft- or rotorcraft-pilot coupling (A/RPC) is an unintentional (inadvertent) sustained or uncontrollable vehicle oscillations characterized by a mismatch between the pilot’s mental model of the vehicle dynamics and the actual vehicle dynamics. The result is that the pilot's control input is out-of-phase with the response of the vehicle, possibly causing a diverging motion. It can also be said that in normal situation, the pilot drives the vehicle, whereas during an A/RPC event the situation is reversed. In that case, the pilot is driven by the vehicle due to this mental mismatch and actively tries to control it Based on the many comments from the industry, [ref. 6] suggested the following ten features (definitions) characterizing virtually every APC documented in the open literature: 1. PIO is a sustained or uncontrollable unintentional oscillation resulting from the efforts of the pilot to control the aircraft. This is the MIL-STD-1797A definition, with the word “unintentional” added. 2. PIO occurs when a response state of the airplane is approximately 180 degrees out of phase with the pilot. It could be any response state of the airplane, the most common for fixed wing aircraft are pitch attitude, roll attitude, and load factor [ref. 6] 3. PIO is an event that results from faulty aircraft design, extension of the airplane’s operational usage into an area for which it was not intended, or following a failure, and is not the fault of the pilot. 4. PIO is commonly found to be related to deficiencies in basic flying qualities characteristics, though it should be treated independently from flying qualities. Most PIOs outside of the research world are related to rate limiting of a control effector or software element upstream of a control effector, but rate limiting can be both the cause of PIO and the result of it. 5. PIO may be either constant-amplitude, convergent, or divergent with time. 6. PIO may be any number of cycles of oscillation; there is no minimum number to declare it a PIO. 7. PIO may occur at very low frequencies – near the phugoid mode in pitch – up to frequencies of around 3 Hz (“roll ratchet”). The most common frequency is in the range for pilot closed-loop control, typically 1/6 Hz to slightly above 1 Hz (1 rad/sec to 8 rad/sec), but frequency alone does not determine whether an oscillation is a PIO. 8. High-frequency, small-amplitude oscillations in pitch (sometimes referred to as “pitch bobble”), and in roll (“roll ratchet”), may be considered a “mild” form of PIO, and may not even be judged as PIO in all cases. If the amplitudes of the oscillations become intrusive on the piloting task, they are PIOs. 9. PIO that interferes with, but does not prevent, performance of a primary mission task is a “moderate” PIO; if a Cooper-Harper Handling Qualities Rating 7 is obtained, it is usually in the range of 4-6 (Level 2 by handling qualities specifications). In general, “moderate” PIO is associated with peak-to-peak angular rates of less than ±10 degrees/sec and control forces less than ±5 lb.8 “Moderate” PIO requires corrective action for normal operation of the airplane, but if it occurs in developmental testing the flight test program can continue. 10. PIO that prevents performance of the task, or that requires the pilot to abandon the task in an attempt to stop the oscillation, is a “severe” PIO; if a Cooper-Harper Handling Qualities Rating is obtained, it is usually 7 or worse (Level 3 or unflyable by handling qualities specifications). Peak-to-peak angular rates are usually greater than ±10 degrees/sec, and control forces greater than ±10 lb, though rate limiting can attenuate the former and result in large increases in the latter.8 “Severe” PIO requires immediate changes to the airplane, and if it occurs in developmental testing the flight test program should be postponed or redirected until the corrections are made. |
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