Yes … that’s what I meant … sorry if that was confusing.
__________
A/R

Not sure what you mean by "fixed distance markers". Do you mean the aiming point markings painted on (catII/III) runways?

Vocabulary approach/landing speeds
 

Boeing says Vref is equal to 1.3 Vs (for the landing flaps configuration).
Those of you adepts of D.P.Davies "Handling the big jets" will also recall his Vat definition, as "speed at threshold"...
At PanAm, we called that speed "Vth" or "vee-thresh".
Vref+5 seems to be the norm of the industry, as the target speed for landing.
Plus winds additives, as described above, not to exceed 20 knots.
And J.T. mentioned carrying Vref+10 for the 727-200. I did that too.
xxx
:ok:
Happy contrails

- and that, in my book, is correct. If the approach is correctly flown, it matters not too much what speed the a/c is flying BEFORE touchdown as it is only the energy AT touchdown that affects landing roll, and therefore that should be correct, I.E. reducing to Vref in the flare and Vref-5 (or as directed) at touchdown.

That will go 99.9% of the way to guaranteeing a safe stop, although as someone else has pointed out, your 'limiting' runway generally allows a 15kt overspeed on those figures. NB NOT a 15kt 'target', just a buffer!

framer, et el “… to confirm that the 'Target Threshold Speed' is indeed Vref+5 on a nice day, and not Vref.” (#37)

In my experience (several operators and manufacturers), ‘Target Threshold Speed’ (TTS) can be used in different ways. Generally, TTS is Vref+5, but this could be a corruption / extension of the ‘calm conditions approach speed’, another ‘target’ speed. Note that the UK AIC (#34) avoids confusion (contention), by using 'basic reference approach speed' (Vref).

The safety view (certification - ignoring add-ons), requires the aircraft to cross the threshold at Vref.
Where manufacturers recommend an approach at Vref+5, then they may have assumed that either the 5kts is bleed off before the threshold, or lost during the landing flare, i.e. a particular technique, not applicable to all aircraft. It might be difficult for a manufacturer to argue otherwise if the aircraft is to retain its certificated landing distances.
If manufacturers do not make these assumptions or have some other justification, then more often than not, the crew’s responsibility for a safe landing is increased by having to consider their ‘calm air’ 5 kt addition in their landing assessment – user beware.

In practical terms for the majority of everyday operations this is not a problem (excess runway length), but occasionally in limiting conditions this small loss of ‘distance’ might be overlooked, which increases the risk of an overrun. (General assumption that +5kts is worth 250ft, but with an extended flare this could be 1250ft; ref AC91-71).
Some regulators/operators accept the status quo without further consideration; the extra 5kts is part of the ‘normal variability in operations’. However, operators should define the non-normal conditions by specifying an acceptable approach and touchdown (i.e. stabilised approach, touchdown position, use of brakes, etc), which IMHO also requires pilots to understand the factors effecting the risks as the conditions change.

BOAC, associating the ‘buffer’ (actually a safety factor in the certificated landing distance) with threshold speed can be misleading. The ‘buffer’ can be associated with any of the ‘normal’ variations in operation, but not all at the same time! A limiting landing cannot tolerate multiple errors, i.e. speed error, height error, touchdown position, spoiler/brake/reverse operation, and runway condition, the latter being one of the great unknowns in aviation.

BelArgUSA “Vref+5 seems to be the norm of the industry, as the target speed for landing. Plus winds additives, as described above, ....”
The UK AIC stresses that any wind addition is added to Vref, not the industry norm (Vref+5).

The short summary is we should follow the advice in the manuals, but use all available information in our landing considerations.

:uhoh:Yes, sorry. Very old habits die very hard (apparently) ... and my excuse is that I’ve been told I was around when dirt was invented.

I am, indeed, referring to the aiming point markings, which used to be called “fixed distance markers” (somewhere, long ago) and are normally painted approximately 1000 feet from the threshold on instrument marked runways.

Thoughts about landing performance...
 

While we are all busy going through the alphabet, with FMS, SOP and CRM...
Any other letters of the alphabet...? How about time to think landing performance.
We all know from initial training that our airplanes are supposed to be landed at Vref.
We know that we land at a Vref that is 1.3 x Vs... and the 20 knots additive.
And we studied that our planes landing performance is based on 60% of the runway bla bla bla...
xxx
Reading our friend IGh here above, he reminds us of the spooling of engines.
Good point.
In many types of airplanes I flew, we had two flaps settings.
The 727 could be landed with 30 or 40 flaps, the 707 did 40 or 50 flaps.
And my old 747 can land with 25 or 30 flaps.
xxx
Not much difference in stall speed between the two... some 5 knots.
The big difference is drag, not lift. The difference is power on the engine.
With extra drag, we keep our engines to higher power. Great for spool up.
Sure it burns fuel, sure it makes noise, but maybe is extra safety, no...?
xxx
I recall the UAL Salt Lake City 727-122 accident, mid-1960s...
Captain approached fast, then went to full idle to reduce speed.
Then when he realized he would not reach the runway he added power.
Too late. The engines did not have time to spool up. He was a former DC6 captain.
In a prop airplane, you want power now, you get it. Not in a jet.
xxx
Then there are the gentlemen here who are shy of "extras" over Vref...
Vref+20 is all Boeing says to add for wind components factor. Fine, no objections.
A little hypothetical landing performance exercise here...
Just for classroom and play with your brains.
xxx
Suppose you land a 747-200 on a long 11,000 feet runway (as usual).
Average passenger weight - say 230 tonnes - your Vref is 134 KIAS.
If landing in a stiff wind, your Vref could be 134+20 = 154 KIAS. Still ok.
So, you good CRM and SOP boys would no squeal a word.
Do you really know landing performance, let us see.
xxx
Suppose same conditions, but the wind is a "very stiff" 60 knots.
Why would I possibly carry Vref+30 then... too fast...?
No, gentlemen. I looked at my landing tables.
I see I could land a heavy 747 at 285 tonnes on this runway (I am only at 230 tonnes)
The Vref then would be 155 KIAS... and I would add 20 knots = 175 KIAS.
xxx
Bottom line is this. Nothing wrong about landing at say Vref+30 (or 40).
That would be Vref+30 = 134+30 = 164 KIAS (I could do as much as... 175)
I consider this... Hopefully dry runway, and still being stopped on 60% of the runway.
Maybe even 70%, as I am not that good, I tend to flare for smooth landing.
Go ahead with your objections - I am retiring and know what I say and do.
xxx
Maybe if the L-1011 (Delta 191) in Dallas would have done so, they might still be here.
And approve.
Extra speed is like extra money in the bank, within reason, and knowing performance.
:}
Happy contrails

Poor spool-up response is generally overrated as a safety issue; the often quoted 6-7 sec is probably the 8 sec certification requirement to achieve ‘landing-climb’ thrust (usually TOGA) from a low power setting (CS 25.119).
Adequate thrust response is available during the approach and landing. Most approaches can be controlled with changes of only 2-4% N1, and this should be sufficient to prevent a sinker during the flare.
One of the tail strike problems is that the sinker may not be recognised; another is the habit of relinquishing control of thrust during the flare – selecting low thrust/idle early or asking the other pilot to control thrust so that a two handed landing flare might be ‘finessed’. These actions may result in the handling pilot attempting to control the combination of speed/touchdown position during a ‘sinker’ with pitch only, usually resulting in a high nose attitude, whereas a small thrust increase might soften the arrival.

Re “Nothing wrong about landing at say Vref+30 (or 40).”
What an appalling statement given to number of fatalities in overrun accidents this year.
Touching down with excess airspeed in many aircraft may prevent the main wheel air/ground changeover working, thus preventing deployment of lift dump/spoiler, thrust reverse, and probably operation of antiskid/brakes. In these circumstances the “knowledge of performance, within reason, or experience – what you say and do” will not prevent an overrun.

yeah that doesn't sit right with me either. It's not the total energy the a/c has that worries me, it's the aerodynamic side of the equation, the lift being generated, weight on wheels etc.
It has made me think though BelArgUSA, thankyou for that.

PEI 3721 -
xxx
Do YOU know how the "air/ground changeover" works in a 747...?
Apparently, you don't...
Also, re-read carefully the presentation of problem... 11,000 ft, dry, etc.
So (1) lack of system knowledge and (2) cannot read and understand.
xxx
:ugh:
Happy contrails

I understand your comparisons of landing weights. I also recognize that you can land on a given runway at some maximum landing weight, with whatever VREF speed that weight would require – then add the appropriate additions for winds and gusts – giving you a “maximum condition” for that particular runway. And I appreciate the fact that if you land at a landing weight less than this “maximum” landing weight, with identical wind conditions you shouldn’t have a problem in getting the airplane stopped once on the ground, even if you flew the approach at the speed that would have been required for that higher, “maximum” gross weight. But that philosophy presumes that you’re going to put the airplane on the ground at the point it should be on the ground – and very often that is not accomplished precisely because of the extra airspeed the guy driving has elected to carry. A given speed in a lighter aircraft is not the same as that same speed in a heavier aircraft. As you undoubtedly know, the handling characteristics and performance are somewhat different. It is also true that if you don’t get the airplane on the ground, it will eat up distance a lot faster by staying in the air – and a faster than required approach is much more likely to result in a circumstance where unnecessarily overflying concrete will occur. Sure, you can plant the airplane at a speed that is a lot higher than what would have been normal, but, you have to know what to do and when to do it. (Personally, I prefer to train the pilot to be able to recognize how to do this – and the procedure I outlined for flare and landing earlier in this thread will allow you to do that.) However, if a pilot is not familiar with the handling characteristic differences presented by flying faster than what the weight requires, and does not know what to do about it when getting down to the runway, the probability goes up rather dramatically that a problem will occur.

Can a pilot do what you have outlined? Absolutely. But because not everyone is going to recognize the performance and handling characteristic differences, I would not recommend anyone doing anything differently than what they’ve been trained to do – compute the required approach speed based on the existing landing weight; fly the approach with the appropriate wind adjustments; reach the threshold with the appropriate airspeed (that means reducing the airspeed an amount equal to the amount added for the steady-state headwind component – keeping any additive for gusts); continue to descend to the runway, flare to reach the level flight attitude with the main wheels just off the runway, take no more than 3 seconds to get the throttles to idle while you continue to descend those last couple of feet – keeping that level flight attitude constant as you descend those last couple of feet; put the mains on the runway while still in that level flight attitude; and quickly fly the nose to the surface.

Please understand … I’m not at all suggesting that you cannot, or should not, fly your airplane the way you fly your airplane. I’m just saying that the technique you’ve outlined is not something everyone should try.

Sorry. On this one I’m going to throw the flag. That was a microburst windshear. It is highly unlikely that even had the flight crew carried an unrealistically high approach speed, the conclusion would have been anything different than the tragedy that occurred. And I certainly don’t want to indicate to some of the younger, more eager, perhaps a bit too self-confident aviators who frequent this forum that windshear is “no big deal,” just add a big handful of knots and press on. That is a sure recipe for disaster that should not stand without a significant and very vocal challenge!

What does the autopilot do during the autoland - vref at 50, reduce idle or touchdown at vref?:ugh:

Although I generally have my eyes closed and hands clasped in front of me in a prayer-like manner, I would say the 737 can land you as low as Vref-10 depending on what happens during the 'flare'. If I were controlling throttle manually I would aim for Vref-5

IGh Re adequate thrust response on the approach (#55).
IIRC this is the basis of being able to fly stabilised approach - the basic control of the aircraft. The magnitude of the thrust change (N1, EPR, etc) and engine response will depend on the aircraft type, but neither the thrust change nor the response time will be ‘excessive’. Excessive is a relative term, but this covered by the certification of the aircraft i.e. the aircraft can be flown/landed “without undue skill” – satisfactory handling qualities, etc, etc. (CS 25. AC 25-7 “flight test guide for certification of transport category airplanes”)

The TC circular focuses on the energy of the aircraft and not the characteristics of the engine response. It specifically defines low energy state as being where “thrust has stabilized in the idle range”, not that the engines might not spool-up quickly. The other low energy aspects are that the airspeed is decreasing and the aircraft is at low altitude.
The low airspeed reduces the option to ‘trade’ speed for increased altitude (reducing the descent rate in the flare), nor can the altitude be traded -nose down- for speed, i.e. the aircraft is low and slow in the flare.
In these circumstances, thrust is the only means of adding energy. A meaningful change (not TOGA) may take 2-3 sec to take effect, and for an average flare time of 7 sec this might not be sufficient to correct the low energy situation.
I do not read the TC comment about ground contact as relating to a tail strike or the severity of contact, only that the aircraft may touch the runway during a late go around from low airspeed. I recall other advice that in such situations it may be necessary to accelerate to the GA (approach climb) speed (~Vref) before attempting the climb away.

I have read, with interest, IGh’s “Examplar for PEI” in which he has pointed out several areas where the FAA (specifically the, Flight Standards offices – the HQ in Washington, and one he referred to as the SW Region) and how those offices have either incompletely addressed the issue of “stabilized approaches,” or have, if I understand his meaning, differing opinions on what that means, or at least, how it is to be achieved. He also has indicated his belief that the US NTSB erred in their investigation of the AA2065 tail strike at Denver in 2006, citing the Chairman’s comment about the board agreeing that the AA’s definition of a stabilized approach not being in “compliance” with FAA Order 8400.10. I’m not sure how that should warrant a criticism of the NTSB, but that’s a discussion for a later time. IGh has also, and very correctly, pointed out that there was a problem in the management of some activities in the SW Region. Since that time, the FAA has apparently taken significant steps to correct the lack of oversight that had apparently existed, according to DFW area newspapers and according to non-attributable confirmations in Washington, by removing and replacing the top two position holders with personnel from other areas within the FAA.

Additionally, some of you may or may not be aware that the FAA Flight Standards HQ office has been engaged for quite a while in updating and modernizing the regulations under which most passengers in the US are carried. You would note that the material that IGh referenced are “orders” and “advisory circulars,” and, as any astute observer or participant in aviation within the US would immediately recognize, the only thing the FAA can enforce are regulations. All the rest of it – including “orders” and “advisory material,” of all types – are recommendations that, while the FAA may believe important, are not requirements that anyone must follow.

You should also know, that, because the US is a nation of laws, it is imperative that the laws that will ultimately govern what happens be subjected to the scrutiny of anyone who may have an interest. It is this process that has lengthened the time that the Flight Standards office has taken to complete this project. Obviously, when anyone attempts to write a “regulation” or a “rule” that is to be followed by everyone, the task of the rule writer becomes more than a bit challenging … as this industry has long ago departed from the idea that a “one-size-fits-all” approach to something like this is not an easy thing to achieve. Also, the speed with which new technology is entering all facets our lives, it is a huge force making its way into the inner most workings of aviation. We are learning more each day about the way people learn to do things … we learn more about how simulation may be used to assist in that learning … we are able to determine, with much greater accuracy today, the root cause of incidents and accidents. And, because all of this is terribly important to the safe operation of aircraft, it is imperative that this material be taken into consideration when the rules and regulations governing the operation of aircraft are levied on those who make their livings in this industry. The rather archaic method in which the US regulatory functions have been mired was beginning to be seen as an “un-indicted co-conspirator,” so to speak, in obstructing efforts to have rules and regulations stay abreast of the situations currently existing in this fast-paced industry.

The FAA, to their credit, I believe, has opted to try a new approach to incorporating into their rules and regulations, a process that sets out requirements in a regulation (a regulation being enforceable) but in a manner that will allow that regulation to be modified rather quickly, when necessary (e.g., learning something new about how pilots learn, or learning something new about why certain accidents occur, or to keep pace with developing technology in simulation, etc.) – while still providing all of the “safe-guards” of having the general public have an opportunity to read and comment on the proposed rules prior to their going into effect. This new approach has been successfully employed in a recent rule on the evaluation of simulators, and, I understand, will be employed in the new rules governing cockpit crewmember training. As a part of that new approach, there is considerable undercurrent in the industry about what it says and what it doesn’t say … but one of the things that it will allegedly contain is a bit more specificity for a “stabilized approach.”

I have learned from someone who claims to know a lot (and has always been relatively accurate in his comments) that the material on stabilized approaches will look like the following:
A pilot flying a stabilized approach must …
1. Have the aircraft in the desired configuration for landing with the engines spooled and stable.
2. Maintain a constant pitch attitude.
3. Maintain a constant heading (within ±10°) or maintain electronic navigation indication with no more than one-quarter scale deviation vertically and laterally
4. Maintain a constant airspeed within +5 and -0 knots.
5. Maintain a constant rate of descent (not to exceed 2,000 fpm below 2,000 ft AGL or 1,000 fpm below 1,000 ft AGL).
6. Keep the aircraft trimmed.
7. Maintain altitude at MDA, when reached within +50 to -0 ft.
8. For constant angle non-XLS approaches (where “XLS” means either ILS or MLS), execute a missed approach when reaching the MDA, DA, or DH (as appropriate – and that is purportedly to mean, if the runway is not in sight or cannot be reached safely).
9. Except where the required visual references for the runway are distinctly visible and identifiable, going below the MDA, DA, or DH prior to the initiation of the missed approach procedure, is unsatisfactory performance.

To maintain my own reputation (such as it is anyway) I can’t guarantee that the above is an accurate listing of what the FAA is proposing, but it does offer an interesting series of steps which we all could, and probably should, contemplate.

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

If you have been in icing conditions for an extended period of time, and at 50ft you fly below Vref, you will drop like stone. The stalling caractristics are based on a clean wing. The 1.30 and (1.23 in fly by wire airplanes) stalling margins will not protect you. I am of the opinion to fly at Vref + all the corrections(wind and gust) and bleed the speed off during the flare and touch down at Vref +the gust factor.
The advantage of reducing the landing distance, by flying below Vref is outweight by the chances of tail strike and reducing the climb performence in case of abort landing.

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:))

tournesol Re – “If you have been in icing conditions for an extended period of time, and at 50ft you fly below Vref, you will drop like stone”.
Your explanation perhaps states the obvious.

Certification requirements cover these points, and require manufacturers to determine any change in stall speed and publish procedures relating to this.
CS 25, AMC 25.21,
4.4.2. c. Changes in operating speeds due to flight in icing conditions.
6.8 Landing (CS 25.125). The effect of landing speed increase on the landing distance may be determined by a suitable analysis.

The AFM or operating manual should have information on the approach and landing speeds (or additions) to be used in icing conditions and the effect on landing distance required.
Some manufacturers have specific speed additives for approaches made in severe icing conditions (where the de/anti icing system can be overwhelmed); again, landing distance corrections are required.

Re “I am of the opinion to fly at Vref + all the corrections (wind and gust) and bleed the speed off during the flare and touch down at Vref +the gust factor.”

This belief might result in an overrun, as all of your excesses will reduce the landing distance safety margin. I suggest that you study the references above and the guidance in ‘Managing Threats and Errors During Approach and Landing’.

[QUOTE][Re “I am of the opinion to fly at Vref + all the corrections (wind and gust) and bleed the speed off during the flare and touch down at Vref +the gust factor.”
/QUOTE]

Safetypee

This is the same advice I have in both our company ops manual and the Boeing FCTM. There is of course the proviso that you have added a maximum of +15 or +20 to Vref depending upon type but that aside I think it is correct.

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.

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.

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”: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: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:Later in 1995, there is this:
On June 26, 1995, the FAA issued FSAT 95-10A,Still later, May 26, 1998, the FAA issued _Flight Standards Handbook Bulletin for Air Transportation _ (HBAT) 98-22,?? 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.

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??

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.

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.

I'm not gonna argue with you all:\

PA:}

edit: some prior thoughts

"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:

http://i675.photobucket.com/albums/v...ponseChart.jpg
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
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
http://i675.photobucket.com/albums/v.../FARsChart.jpg

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:

http://i675.photobucket.com/albums/v...DAcceljpeg.jpg
[above] “727 Ops..." _Boeing Airliner_, Jan-Feb'66,pg5: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.]

http://i675.photobucket.com/albums/v...celaration.jpg

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:
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.

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?

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:"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 thatThere 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.

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.

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

From a statement in slot just above: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: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/

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."

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.

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 ...

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'.

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?

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:ok:

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

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 ?