Vref & landing

[AirRabbit]

Originally Posted by RansS9

Dear AirRabbit,
I read your article on final approach / flare...it's great. On your scale C150 to 747 I'm definately at the low hours C150 end. However I'm slightly confused...a not unusual situation. Two points
a) I've got three seconds to retard the throttle and remove any crab. Does the three seconds start when I start to initiate the flare or when I achieve the level flight attiude?
b)Is the gust factor that's added the total gust or the component along the runway?
Apologises if this is all blindingly obvious.
TIM

Originally Posted by framer

Dear RansS9,
If you are a low time pilot just do exactly as you are being taught by your instructor. Don't muck around with final aproach speeds etc. Wait until you have 1000hrs then revisit the idea.(Unless Airrabbit is your instructor of course)

Hi RansS9:
It's nice to know that there are those on this forum who think very much alike - and, actually framer beat me to the punch (thanks framer!) He is exactly correct. I never recommend anyone doing anything contrary to what they are taught by their instructor or going against the dictates of their company policy.

Your question is a good one and the answer is that you should take approximately 3 seconds to flare and then not more than 3 more seconds to get the power to idle - and reaching idle should occur at the same time as the mains touching the runway. But, again, if you're working with an instructor, don't attempt to do this without discussing it with him/her. If you're really driven to try it and you're not working with an instructor now, what you may want to do is to discuss this with an instructor and ask him/her to go along with you while you work on the techniques involved. My point was to get folks to recognize that the proper attitude to touchdown is the level flight attitude for an established speed/configuration ... and that should put you comfortably between Vstall and Vref.

If you’re holding a crosswind correction (a crab), that correction is removed as you flare (as you have recognized) – and, here is one of the times when more rapid throttle reduction MAY be warranted. The longer you stay in the air, the more time you give the wind to work on your position. The closer you are to the runway when you complete the flare and pressure the nose around to align with the runway, the quicker you can get on the ground – out of the air – and limit the time that the wind can work on your position. No doubt you will want to apply some “upwind” aileron to keep the forward sweeping wing from rising as it moves forward – but if the wind is strong, you might have to put a bit more aileron control into the wind – and wind up with a very slight bank angle into the wind. If necessary, this may cause you to wind up touching down on the up-wind wheel(s) first … but if you’re in a very shallow bank, by the time the gear struts retract (or the springs begin to give) that should put the down-wind wheel(s) on the surface pretty quickly.

When I taught in transport category airplanes, I used to get my students to understand what attitude I was describing by having them fly down the length of the runway (at 1 to 5 feet above the runway) at the speed reached after completing the flare ... which requires adding a bit of power to keep that airspeed. Then, when they had that part pretty well under control, I'd ask them to do the same thing - attempt to fly down the length of the runway (at that same 1 to 5 feet) - but I wouldn't let them add any power. Guess what? Without that additional power and by staying in the level flight attitude - the airplane cannot maintain level flight ... it will descend. And when it descends that 1-to-5-feet, you land - and the airplane is in the proper attitude to do that. Of course, with any power added, the touchdown is usually very soft and very "greasy," and much farther down the runway than you would want. THAT is NOT what I was teaching. The point was to show that keeping the level flight attitude is not going to allow you to climb AND perhaps the most significant point is that the student learns to use whatever cues is logical to use to achieve and maintain that level flight attitude. When you flare, immediately reduce the power to idle (getting to idle as the wheels touch – and you can do it quickly or take up to 3 seconds, depending on the conditions) results in a firm (not hard) landing – firm enough to get the wheels on the surface (and through water, snow, ice, etc.) with an attitude that still allows airflow over the tail (for directional control until you get the nose gear on the ground) and because the nose is not way up there, you can fly it to the runway pretty quickly – and have that nosewheel steering available that much more quickly.

I used to teach my students to land the way I landed. I land fine (at least I think I do - haha). So ... how come they couldn't do it? Well, different pilots use different input cues to determine what to do with the airplane at different points … when to do it, how much to do, when to take out an input, etc. So I adjusted my teaching approach and decided to let the students figure out what cues were best for them to use to flare to "a level flight attitude" ... They may find that what I use works for them – but they may not – and I found that it was mostly NOT. Therefore, because I wanted them to determine what cues they thought were best to maintain that attitude without having to do it by reference to the attitude indicator or altimeter, I didn’t tell them I was teaching them to find the level flight attitude, I merely told them to fly down the runway – without climbing … without descending … without accelerating … and without decelerating. What is the definition of “level flight” again? I wanted my students to fly the airplane as well as they could - not necessarily the way I fly the airplane. And when they find out what works for them ... it DOES make a difference!

So, again, as framer said, if you’re working with an instructor –don’t mess around with this – do what your instructor teaches you to do. If you’re not working with an instructor and want to try out this method, I’d recommend getting with an instructor and tell him or her what you want to do … and then go from there. Most instructors will be willing to see what it is you’re describing, if they don’t already do something similar. Let me know what you decide to do.

[safetypee]

Stan Woolley #67, an interesting point, which is similar to many disparities in the industry. The problem might originate with:-

• The aircraft certification standard may be pre regulatory change - Older aircraft – ‘Grandfather Rights’. This could mean that the risks associated with landing differ from those in a modern aircraft.
  Alternatively, the aircraft may be using a different standard of landing performance, or that the aircraft is not affected (unlikely).
• There might be disparity between certification and operational requirements, either within the manufacturers documentation, or the certification and/or operational regulations.
• Manufacturers and/or regulators might assume a landing distance additive is used in icing conditions, i.e. it’s the operator’s responsibility for compliance with (safety) regulations.
• There could be problems of communications; cf TAM, Spanair accidents, where ‘lost’ or corrupted operating information from manufacturer / regulator can contribute to an accident; – check for old notices to operators, advisory manual revisions, etc.

So it might not be surprising for manuals to have differing standards, but what is consistent is the operator’s responsibility for a safe operation, which comes down to the Captain’s responsibility on the day. Thus, it is important to understand all of the aspects which could affect the landing, the assumptions made in the regulations, and the risks involved. A good reference which covers normal operation is the UK AIC (#34) and also the relevant certification standards i.e. CS 25, FAR 25.

[IGh]

Spd Control, TURBOJET ops, "engines spooled-up"

First, an easy question, for “AirRabbit”, about something you mentioned in slot #62, thrust – energy management proposal for “stabilized approach”:

“… a bit more specificity for a “stabilized approach.” … the engines spooled and stable.” [???]

There it is again! “stable” thrust???
AirRabbit, Where are you getting this? The airline pilot has always been free to move TURBOJET’s Thrust Levers while on final.

The “Energy Management Element” of FSF’s ALAR TASK FORCE [ALAR Briefing Note 4.2] doesn’t say anything about “stable” thrust. Nor does FAA’s AC120.71, Appdx 2. Nor does 8400.10.

I’m curious about where you get this notion about “stabilized thrust”??? Is there something from FSF? Maybe from FAA Flight Standards? Or, maybe this is another “alternative” from FAA’s SW Region?

= = = / / = = = =

This thread is about Approach Speed. Our industry previously debated factors that affect a pilot’s ability to control that SPEED during “unusual” conditions (fatal 11Nov65, and inflight breakups post- ARC-events). The TURBOJET engine as used in civil ops (lacking the engineered safety feature of Thrust Attenuators), still suffers the spool-up delays of decades past. To insure that any THRUST LEVER advances of a pilot yield a more intuitive linear THRUST response from his TURBOJET engines, the “engine spooled-up” criteria was established for use during final approach.

Contributed by “AirRabbit”, in slot #62, dated 22nd November; regarding
-- any US airline and it’s regulator
-- FAA’s 8400.10 and
-- FAA’s “standards” for airline pilots:

“… the material … referenced are “orders” and “advisory circulars,” … in aviation within the US … are not requirements that anyone must follow….”

Hmmm, not a requirement?
The FAA’s “standard” for AIRLINE pilots employed by US operators, re’ “stabilized approach” is published in 8400.10.

As you’ve asserted (as did FAA's AFS-2 Flt Stds), FAA’s SW Region seems free to disregard the engines spooled-up “standard” included in FAA Order 8400.10, meant for checking US air carriers. An alternative “standard” was created by an operator, and accepted by FAA’s SW Region. The operator did something more, operator cited FAA’s 8400.10 as the source for that “alternative” standard, a deception inflicted upon their own instructors and Check Airmen.

FAA Order 8400.10,
_Air Transportation Operations Inspector's Handbook_, Volume 4, chapter 2, section 3, paragraph 511 discusses stabilized approaches [8400.10 CHG 10 page # 4-158, left column, on FAA web-site, page dated 12/20/94,]
http://www.faa.gov/library/manuals/e...4/4_002_03.pdf

Paragraph 511 defined a stabilized approach, for TURBOJET ops’ it established the old “engines spooled-up” as the FAA’s standard, then in the right column has this note to POIs:

“NOTE: Principal inspectors shall not approve an operator’s procedure unless the stabilized approach concept is used for all turbojet aircraft operations....”

Later in 1995, there is this:
On June 26, 1995, the FAA issued FSAT 95-10A,

“The ‘stabilized approach concept’ of 8400.10, [paragraph] 511, will be considered essential for safe operations for all aircraft in air carrier operations....”

Still later, May 26, 1998, the FAA issued _Flight Standards Handbook Bulletin for Air Transportation _ (HBAT) 98-22,

“… 3. ACTION….
"B. POIs shall ensure that their operator's operations ... manuals contain criteria for the stabilized approach as referenced in FAA Order 8400.10, Air Transportation Operations Inspector's Handbook , volume 4, chapter 2, section 3, paragraph 511. …”

“… POIs shall make a PTRS entry to record the actions directed …”

?? AirRabit? That FAA standard, only in 8400.10, is not a requirement?

For SMS gurus, ?? does an airline management pilot have an obligation to comply with such an FAA "standard", even when his local regulator accepts non-compliance? Lacking an "accountable executive", maybe the very big US airlines are designed to overlook such details, and avoid such "changes" to their manuals: the airline is so big, there is no manager to take charge, no manager obligated to insure compliance.

[AirRabbit]

Originally Posted by IGh

First, an easy question, for “AirRabbit”, about something you mentioned in slot #62, thrust – energy management proposal for “stabilized approach”:
“… a bit more specificity for a “stabilized approach.” … the engines spooled and stable.” [???]
There it is again! “stable” thrust???
AirRabbit, Where are you getting this? The airline pilot has always been free to move TURBOJET’s Thrust Levers while on final.

Hello IGh. Thanks for the “soft ball,” I think. Since you didn’t question the use of the term “spooled,” I’m presuming that this particular term doesn’t engender the same degree of animus as the term “stable” does; however, at the risk of providing an overly simplistic answer, the term “stable” (as in “stable thrust”) does not mean to “lock the throttles and don’t touch them again.” It is a term that is often used with respect to throttle usage as one where the movement of the throttles may be continuous or constant but the overall effect is one that results in minor changes in pitch, trim, or airspeed – usually involving movement of the throttles significantly less than a full “knob-width.” Lack of stability in thrust would be evident in a rather large variation in pitch, trim, or airspeed – with airspeed likely being the most noticeable – exceeding values of 4 or 5 knots – strictly as a result of throttle manipulation. I probably need not say the words, but to preclude any misunderstandings, the term “stable thrust” is meant to be the opposite of “unstable thrust,” where power management runs the gamut from “flight idle” to “takeoff thrust,” in wide-ranging and precipitous throttle … (shall I say) adjustments??

Originally Posted by IGh

I’m curious about where you get this notion about “stabilized thrust”??? Is there something from FSF? Maybe from FAA Flight Standards? Or, maybe this is another “alternative” from FAA’s SW Region?

Well, your reference to the US FAA Advisory Circular (AC) 120-71, is a good reference, and, while the term “stabilized thrust” is not used, certainly the terms “stabilized approach” and “stabilized condition” are used throughout. If you have the problem you seem to have with “stabilized thrust,” I would be curious to know if you have the same problem with either “stabilized approach” or “stabilized condition.”

You may desire to review the document you referenced, AC 120-71, Appendix 2, in which a “stabilized approach” is described a bit more … and, among other things, are the following 2 statements contained in a description of a "Stabilized Approach:"

“The airplane speed is within the acceptable range specified in the approved operating manual used by the pilot.”

...and

“Power setting is appropriate for the landing configuration selected, and is within the permissible power range for approach specified in the approved operating manual used by the pilot.”

It would be from these 2 sources that the radical concept of “stabilized thrust” derives … and please note the reference to “speed range” and “permissible power range” – clearly denoting the ability to actually move the throttles. It’s something very similar to the admonition to maintain a “constant angle, constant rate of descent;” which, of course, under any interpretation, we would all recognize as being similarly not possible – if taken to the dictionary definition, as written.

Originally Posted by IGh

Contributed by “AirRabbit”, in slot #62, dated 22nd November; regarding
-- any US airline and it’s regulator
-- FAA’s 8400.10 and
-- FAA’s “standards” for airline pilots:
“… the material … referenced are “orders” and “advisory circulars,” … in aviation within the US … are not requirements that anyone must follow….”
Hmmm, not a requirement?
The FAA’s “standard” for AIRLINE pilots employed by US operators, re’ “stabilized approach” is published in 8400.10.
As you’ve asserted (as did FAA's AFS-2 Flt Stds), FAA’s SW Region seems free to disregard the engines spooled-up “standard” included in FAA Order 8400.10, meant for checking US air carriers. An alternative “standard” was created by an operator, and accepted by FAA’s SW Region. The operator did something more, operator cited FAA’s 8400.10 as the source for that “alternative” standard, a deception inflicted upon their own instructors and Check Airmen.

Originally Posted by IGh

?? AirRabit? That FAA standard, only in 8400.10, is not a requirement?

First, I think you may have confused me with someone else. I don’t believe that I’ve ever asserted that anyone is free to disregard any issue that is pertinent to aviation safety. If your intent here is to criticize the SW Region office of the FAA – I’ll offer to hold your coat and hat while you do so. But if your intent is to berate my understanding of Federal Aviation Regulations vs. Advisory Circulars, Bulletins, FAA Orders, and the like, I’m afraid I’ll have to take exception. The only regulations the FAA is charged with enforcing (indeed, the only ones they MAY enforce) are those published as regulations – and they can be found in the Code of Federal Regulations. Forgive me if I sound like a colonist, but rules are rules, and advice and preferences are not - ACs are not rules; 8400.10 is not a rule. The SW Region wound up getting a lot of light and heat because of the way some there elected to do business. I am, and have been, of the opinion that the duty and responsibility of any regulatory authority is to set the minimum standards that have to be met – where, if such standards were only met in a minimal way, that level would provide for safe operation of the airplane. If the regulator can show why something is necessary to accomplish – fine – they should do so. If they cannot show why something is necessary, they have no business trying to convince, cajole, threaten, induce, persuade, or encourage anyone to do whatever it is. Now, having said that, I also believe that it is the duty and responsibility of everyone in the aviation industry to try to do the best they can for all concerned. Normally, the most efficient way to operate an airplane is also the most advantageous for maintenance, scheduling, profit, and … safety. No one should have to be encouraged, persuaded, induced threatened, cajoled, or convinced to operate an airplane safely.

However, as I often say on these threads – anyone here is free to disagree with my opinions – and some do – regularly, in fact. However, the fact remains that what is true is not dependent on any particular person’s agreement with that truth. The other fact is that when a pilot is in the cockpit, the way he or she actually flies the aircraft is a matter of personal pride and professionalism (modified, of course, by whatever the bloke in the other seat might have to say).

I would hate to find this industry in a state where the only thing anyone does is just (and only just) what he or she is required to do. I’m not a particular fan of having the kinds of skills tests to which I’m likely to be subjected contained in an internal document published only to those who may administer that skill test and determine my future. I think the new approach that some in the FAA have described sounds at least interesting … and I, for one, am anxious to see what it is they are proposing. Over the years, I’ve met several FAA employees – and generally, they pull their britches on the way we all do … and I would think that a couple of “enterprising” dolts who managed to approve some funny (“funny” as in “strange”) goings-on in the SW Region, does not make the rank-and-file FAA employee very proud of his or her colleagues.

[Pugilistic Animus]

I'm not gonna argue with you all

PA

edit: some prior thoughts

Your aim with a large aircraft is to ALWAYS be trimmed and stabilized---during all phases of flight--furthermore---the most important aspects of being 'stable' seems lost in certain SOPS

you should be able to:

Arrive over the threshold at Vref [in most case] at the correct height---in such a manner as to assure a touchdown in the TDZ---

and maintain a thrust setting that allows full thrust to be available before contacting the ground--- i.e a missed approach or landing climb-or turbulence/shear [added words bold]--i.e spooled up in time to avoid a crash!!!

PA

[IGh]

"Stabilized Thrust" ??

AirRabbit -- that's a long one, yours in slot #71 above, you seem OK with that "alternative" standard, where operator avoids the "engines spooled-up" requirement.

Take that exemplar case noted several slots above: DEN06IA051

Those mishap pilots flew their final approach using their company's "alternative" standard -- at a "stabilized thrust" [NTSB cites the EPR as steady at 1.1 EPR all the way to impact].

?? Per the FAA's standard, should such an approach have been continued below the 500'AGL "gate"?

AirRabbit --
-- How does YOUR understanding of the FAA's "engine spooled-up" requirement fit with that operator's alternative "stabilized thrust"??

-- Do you think that "alternative" standard was an effective guide for those mishap-pilots??

Those mishap pilots did just what their company told them to do, at their company's "stabilized thrust". Speed control becomes quiet difficult using that "alternative" standard, when the engines took seven seconds to spool-up.

EDIT -- to add ENGINE ACCELERATION curves, for display on the web: First is a generic response curve (Airbus & Boeing agreement) for a 1990's TURBOJET:


Flight Safety Foundation’s ALAR Tool Kit
ALAR Briefing Note 4.2 – “Energy Management”
Figure 3: “Typical Engine Response From Approach-idle Thrust ...” “Engine Acceleration

“When flying the final approach with the thrust set and maintained at idle (approach idle), the pilot should be aware of the acceleration characteristics of jet engines (Figure 3).”

FSF, _Flight Safety Digest_, August-November 2000, pg 75-79 [five pages]
Flight Safety Foundation, Approach-and-landing Accident Reduction (ALAR) Task Force.

Here's the FAR req'd response


Below is result of the accident at SLC on 11Nov65, Boeing's first graphics to teach airline pilots about the weaknesses of the TURBOJET engine:


[above] “727 Ops..." _Boeing Airliner_, Jan-Feb'66,pg5:

“Engine acceleration from 47% to 100% thrust requires approximately 2 seconds. During acceleration from idle, power increase after 2 seconds is negligible, after 4 seconds is only 20%.”

Turbojet "Spooled-up" concept

During first week of training for TURBOJET pilots, airline must introduce the "spooled-up" concept for TURBOJET's "stabilized approach" STANDARD (see B727 / 11Nov65 fatal accident at SLC). Other airlines taught 50%N1 as their "spooled-up" standard for the JT8D. [NOTE: This really teaches pilots about DRAG required, to attain "spooled-up" requirement, prior to 8400.10's 500' gate.]

[AirRabbit]

Originally Posted by IGh

AirRabbit -- that's a long one, yours in slot #71 above, you seem OK with that "alternative" standard, where operator avoids the "engines spooled-up" requirement.
Take that exemplar case noted several slots above: DEN06IA051
Those mishap pilots flew their final approach using their company's "alternative" standard -- at a "stabilized thrust" NTSB cites the EPR as steady at 1.1 EPR all the way to impact

I don’t see what would allow you to come to a conclusion that I “seem OK” with some nebulous “alternative standard.” If you read the post I made earlier, the first item I indicated as being acceptable is “Have the aircraft in the desired configuration for landing with the engines spooled and stable.” In my follow-on post (immediately above) I attempted to point out the fact that “stable thrust” doesn’t mean “not moving the throttles.” The last time I checked, an EPR reading in the neighborhood of 1.1 was very close to “idle” – and I certainly hope you don’t think that maintaining a stable, idle thrust on final is an appropriate way to get the job done!

If you are questioning the decision of the crew, who seem to have accepted what the airplane gave them, i.e., a speed, rate-of-descent, a ground track, etc, I agree with your puzzlement. Just because they maintained a “stable thrust setting” doesn’t mean that the setting they decided to use was an appropriate thrust setting – and – I’m completely in the dark about why you think I think that is OK!

In my post (immediately above) I indicated that “(the) airplane speed (must be) within the acceptable range specified in the approved operating manual used by the pilot” …and…“(the) power setting (must be) appropriate for the landing configuration selected, and (must be) within the permissible power range for approach specified in the approved operating manual used by the pilot.”

I think for you to presume that the flight crew was flying a procedure their company mandated or approved, when they maintained essentially an idle power setting all the way down final, is a bit of a stretch. Of course without “being there,” its hard to know just what the crew was thinking … but, and excuse me if I step on some toes here, but it seems as though the crew was deliberately attempting an “idle approach, flare, and touchdown.” I can’t imagine any company, anywhere, thinking that this is an acceptable procedure. In my opinion, this is an air-show, glitzy, "gee-wiz" stunt that has no place in air transportation service! In fact, the link you provided describes the company’s procedures as the following:

A stabilized approach means the airplane must be: at approach speed (VREF + additives); on the proper flight path at the proper sink rate, and at stabilized thrust. These requirements must be maintained throughout the rest of the approach for it to be considered a stabilized approach. If the stabilized approach requirements cannot be satisfied by the minimum stabilized approach heights or maintained throughout the rest of the approach, a go-around is required.

In my opinion, this sounds like a very logical, very safe, and completely appropriate procedure to follow. However, what the crew flew was not this procedure. Where you get the idea that the crew followed an authorized or approved “alternative” procedure is beyond my understanding.

Originally Posted by IGh

AirRabbit --
-- How does YOUR understanding of the FAA's "engine spooled-up" requirement fit with that operator's alternative "stabilized thrust"??
-- Do you think that "alternative" standard was an effective guide for those mishap-pilots??
Those mishap pilots did just what their company told them to do, at their company's "stabilized thrust". Speed control becomes quiet difficult using that "alternative" standard, when the engines took seven seconds to spool-up.

And what makes you think that this crew “did just what their company told them to do?” Do you have any statements? Any manuals? Any bulletins? Any anything? Are you of the opinion that the company lied when they supplied the definition of a “stabilized approach?”

The concept of having the engines “stabilized” within an appropriate power range to provide adequate speed and rate-of-descent … and the concept of having the engines “stabilized” at idle power … are completely different issues – and I cannot imagine that you don’t see that simple fact. I continue to puzzle over the fact that somehow you think that I believe an “alternative standard” or an “alternative procedure” is even a discussion issue here. The flight crew had an established procedure. They did not follow that procedure. That part seems pretty evident. Simply because they did not follow the established procedure, does not immediately imply that they were complying with an acceptable or an approved “alternative procedure” – unless you have access to information that no one else has … is that the case?

[IGh]

engines "spooled-up" NOT at "stabilized thrust"

OK -- this is STILL about control of Approach Spd on TURBOJET aircraft. There is a tightly coupled relation between Vref, and Engines "SPOOLED-UP".

Reply to a question posed in the slot above:

"... you of the opinion that the company lied ... the definition of a 'stabilized approach'?...”

"Lied"? Maybe the operator never appointed the "accountable executive" to coordinate the needed changes to their manuals. Even in good time$, the operator never wanted to participate in projects motivated by their own A&L mishaps. Sure, they'd send a few staffers, but never wanted to train their managers to ALAR Standards. Nor did their local regulator provide training for the CMO guys, even after the Recommendations following a mishap at LIT [Recommendation A-01-69 is classified "Open--Unacceptable Response."]:

Even now the SW Region & the AA-CMO think that

"... stabilized thrust has the same meaning as engines spooled-up" [2Jan08 reply from Flt Stds' AFS-2].

There is a longer paper trail on this subject of "stabilized approach" criteria re' that operator. There were several investigations, the ALAR Task Force, repeated Bulletins to the CMO/POI, but the operators' CMO never was capable of persuading the operator toward correcting the err re' their 8400.10 deception. The Board gave up on trying to get the regulator to work with the operator to get their manuals corrected.

[AirRabbit]

Hi IGh:

Perhaps you are used to speaking or writing with multiple abbreviations, being under the assumption that everyone surely knows the meanings of such references. If I may, here is a suggestion … it would aid the readers if you were to indicate what it is that you are using when you abbreviate terms … e.g. it would have been helpful to have indicated that the “ALAR Task Force” or the “ALAR Standards” referred to the Flight Safety Foundation’s “Approach-and-Landing Accident Reduction” efforts. It took me a while to locate the appropriate references.

Additionally, you cite sentences supposedly contained in a letter from an official in the FAA’s Flight Standards Service, but don’t give the reference(s) where one can read the entire letter, including the referenced sentence(s), to learn the context in which it(they) were(are) used. Additionally, you claim to know a lot about the exchanges that took place between the respective FAA offices and the offices at American Airlines; you suggest that you understand the motives behind some of those exchanges; and you seem to be certain of the failure of some of those exchanges. I understand if your anonymity is necessary to provide this information without incurring recriminations, but, please understand the awkwardness in which your readers are finding themselves in trying to keep up with your allegations.

I continue to suspect that you believe that 1) American developed a procedure that ultimately turned out to be inappropriate – and 2) the local FAA office is complicit in accepting (or approving?) that procedure. However, I cannot understand why you believe this is true. You cite an example of a flight crew flying an approach that is contrary to the procedures that American stated was the appropriate and approved procedure. If I’m reading the American procedure correctly – they required a “stabilized approach,” which they described as having the airplane at the proper approach speed (Vref + additives), on the proper flight path, at the proper sink rate, and at stabilized thrust. Apparently, the FAA office agreed with the procedural description provided by American. I’ve attempted to provide a rather universally practical understanding of the term “stabilized thrust,” that does not imply a rigid, unmovable throttle position at any power setting. Rather, the throttle setting has to be in a range (indicating that movement is logical and is to be expected) appropriate to the airspeed and rate-of-descent desired due to glide slope angle, configuration, and weight – and, I was hopeful that anyone would understand that such a “throttle position range” would not be “idle thrust” – hence the descriptive term “spooled and stable.”

I believe that you think there was a sinister effort on the part of either American or the FAA to provide American crews with an incoherent description of how an approach was to be flown – and it was this incoherent description that caused confusion and resulted in the flight crew mishandling the approach. I would submit that your conspiracy theory is just that – a conspiracy theory – that has no place in a legitimate discussion of approach procedures. Unless you can provide any information to the contrary, I would suggest that you cease with the non-specific allegations of wrong doing on the part of the company or of the FAA – heaven knows, the FAA in the SW region has enough of its own problems without having to deal with conspiracy theories as well.

[IGh]

The Alternative Standard vs FAA's "engines spooled-up"

From a statement in slot just above:

"... cite sentences ... in a letter from an official in the FAA’s Flight Standards Service ... the reference(s) ..."

The ref # used by FAA for that reply-letter is "reference: S20070716012": Letter from FAA, John M. Allen, Deputy Director,[AFS-2], Flight Standards Service, Reply Dated Jan 2nd, 2008. Letter was 2-pages; one important paragraph is the last paragraph on the first page:

“In its review of these complaints, Flight Standards Southwest Region determined that ... the term “stabilized thrust” ... has the same meaning as engines spooled up and can be used ....”

Edit: FAA's website shows that the writer [FAA, John M. Allen, Deputy Director,[AFS-2], Flight Standards Service] was later PROMOTED to AFS-1, and as of Feb'09 that man is listed as "John Allen, Director, Flight Standards Service"
per: http://www.faa.gov/about/office_org/headquarters_offices/avs/key_officials/

[AirRabbit]

Hi IGh:
Ummm... thanks for the reference. Now that you've provided a reference number for the letter you describe, I've got just one question ... do you have a suggestion as to where one would search for that reference number? Just for your information, both a "google search" and an "FAA search" for that number resulted in "no match found."

[tournesol]

Safetypee,
Tx for the link. It is indeed educational and a refresher for the more seasoned aviators. Throughout, I have not seen anywhere suggesting to fly below Vref.
My opinions have been formed by following the guidelines from Boeing training manuals.
I have flown in the corporate aviation for a while,where the idea of flying below Vref is quite readily accepted. Personally, I have yet to see any publication by any manufacturer sugesting this technique. Even though a lot of non FAA/CAA approved publications, TRIs and LTCs encourage it.
As for my exposures to airlines, this is not tolerated by the major manuacturers nor by any airline that I know of.
By following the recommendations of those who build and certify the planes that we fly will keep us safe and legal.

[john_tullamarine]

where the idea of flying below Vref is quite readily accepted

How quaint .. can't say that I'd like to be in the box at a post mishap inquiry trying to defend such a practice ...

[BOAC]

Good job you were not involved in autoland certification for the 737, JT - it often (naturally) touches down at speeds a fair bit below 'Vref'.

[safetypee]

tournesol, to avoid any misunderstanding about landing from Vref-5 at the threshold; I stress that the certification tests only demonstrate that a landing will be safe, and thus provides a margin of safety below the normal minimum speed of Vref at the threshold. Vref-5 is not intended for normal (or even abnormal) operations, only as a margin to counter speed inaccuracy, wind, etc.

It would be interesting to understand why manufacturers and operators add an additional margin above Vref for normal landings. It could indicate a difference in views of the safety margin between the operational and certification assumptions. If Vref is ‘safe’, and landing performance is based on this, then what is the justification – the balance of safety from the speed margin in landing at Vref+5 against a reduction in the landing distance safety margin?

[Pugilistic Animus]

Vref is safe the arrival in the TDZ at between Vref an Vref+5 is to me a common sense item---under most circumstances however ---see BelArgUsa's post

as long as you are not accelerating [in the real meaning] you are in steady level coordinated flight---if parameters are changing VS/ ASI then you are not in 'SLCF' however if [in my divination] have allowed yourself the correct altitude/airspeed buffers it is possible to alter the flight path and resume SLCF---by making trim and power changes------

but that is steady level coordinated flight


---to be stable for landing you must first acheive force vector equilibrium, thence remain with in the performance parameters dictated by the OEM/certification authorityn and the Air carrier rules and coomon sense

now, many folks get SLCF confused with stable they are different --- One can be stable at VMO


However,

----by acheiving and remaining in SLCF the are several benefits acceleration noted on the instument give advance notice of event like gust or windshear

----engine thrust should be quite close to that required for fast spool up to aprch and ldg climb thrust form Vref+x

correction to mild deviatons in sink rate are easily adjusted for with thrust because the airplane will remain near trim airspeed and -- if applicable-- it makes the ol' "boeing push' real smooth like if you're gonna get an arrival you can just drag her on in
PA

[john_tullamarine]

Good job you were not involved in autoland certification for the 737

Have no difficulty with a below approach speed touch down .. if this isn't the case then something strange is going on .. unless one is coming aboard the boat. However, approaching at below Vref for a normal civil aircraft is an invitation for legal sanction somewhere down the track after it's all turned pear-shaped.

One of the reasons we see a basic additive is to provide for handling differences between the stall/min speed certification animals.

For example, if my recollection is OK, the 727-100 was a older conventional stall certification while the -200 was to the later rules. End result was that the -100 was fine at or around Vref but the -200 behaved itself better if one carried an additional 5-10 knots .. while the aces could get away with the lower speed ... those of us who aspired only to a routine stick and rudder standard preferred to avoid the near inevitable crashes when the ground rose up to smite the aircraft ... always amazed me .. the -100 was a pussycat delight to land (greasers were the routine norm) while the -200 had to be watched all the time (in 2500 hours I managed one greaser and I still have no idea how that occurred .. perhaps the ground was having a day off that day ?

I occasionally reminisce about a chap with whom I flew for a few months .. his worst landing generally was far better than my best .. I could never quite work out just how he caused the -200 to cease going down and commence rolling along the runway with no generally discernible flare or touch down dynamics ... then, again, he had about a million hours on the -200 so that may have had something to do with it, I guess ?