B737 Gust correction
 

I have only been on the B737-300 for a few months and have been given different opinions by different captains, each wanting me to adapt to their methods. I'm trying to look for the pros and cons for the points below

In the company that I work for there are two opinions on gust corrections.
many of the pilots believe that Vref +15 knots is sufficient, even though the book states Vref+20 as the max limit.

Also when windshear is reported what is your companies policy regarding flap settings. I always thought a larger flap setting would be better as it allows the engines to be spoiled up more. Do you use Flap 30 or 40?

What do you do?

There should be no different opinions between "captains" on how to apply gust factors or landing flap positions. It is all laid down in the Boeing 737 FCTM. Those individuals who choose to disagree from the Boeing recommendations should have the bottle to write to Boeing tell it to change the manuals. There are far too many "experts" ready to rubbish Boeing recommended procedures.

Wind Corrections
 

Gravox,

With regard to 'what to do'....

Read, learn, live your company's SOP. Study, learn, love your company's SOP.

The advantages of flying a 'roll your own' operation.....Uh, let me think....Uh.... (can't think of any off the top of my head.)

The disadvantages of not following your company's SOP to the letter: (You fill in the answer...)

When you fly with certain captains who 'suggest' other ways to fly the aircraft, politely decline. With captains who insist you fly it 'their way', tell him "You have control, I have communication." (Then, make standard callouts!)

With regard to windshear and either mandated or recommended flap setting...uh, let me see...uh....Oh yes, please consult your SOP.


Good luck with your standardized operation!!!!!


I've been an airline captain for 22 years now, and I've NEVER critisized a first officer for following the SOP. In a list of major 'wrongs' a captain can commit, that's gotta be in the top five.

PantLoad...

Your company's SOP dictate how your aircraft should be operated. If a captain desires otherwise, give him/her the book and ask for a chapter/section/page reference where he/she may deviate there from.

my company's SOP's dictate to use F30 in gusty conditions,F 40 are used in short runways and/or high weights.Don't forget that F 40 give a tremendous increase in drag so F 30 are preffered in windy conditions as there is more thrust available for acceleration.
I couldn't agree more with the other gyus and especially with A37575,no one is allowed to make suggestions or speculations of his own.Also my dear friend keep in mind that if you attempt a landing at the notorious airports (for their windy conditions)of Rhodes,Heraklio or Samos with only Vref+15 and not Vref +20 or flap placard speed- 5 (whichever is more limiting)you could find your self in trouble........

I suspect that there have been several threads on gust additives; however, it might be worthwhile going back to basics.
Here are some that I recall:-
The aircraft certification will have demonstrated a landing at Vref-5 (at the threshold).
Most manufacturers accept that a normal approach speed (e.g. Vref+5) is an average speed datum and not an absolute minimum. Vref should provide aprox 20% speed margin above stall warning (stick shake) and 30% above the stall.
Aircraft stall, and thus stall margins are related to AoA; not all gusts will result in a AoA change proportionate to the indicated speed change, i.e. the gust may not be as severe as indicated by speed.
The performance certification normally assumes a speed loss of 7 kts in the flare.
The 'operational' margins in landing distance assume a maximum deviation of +15kts at the threshold. This margin also considers other aspects such as height above 50ft, reported wind error, etc, but these errors are not considered in combination, i.e. not high and fast together. Consider runway length required, add a margin if advised by the manufacturer e.g. increase distance by 2% for every kt above vref+5. The assumptions about performance on a wet runway provide lesser margins and there is no margin on a contaminated runway. Check runway length required / available very carefully.
The reported wind gusts are normally associated with 50ft near the runway. Thus the conditions earlier in an approach may not indicate the landing conditions – generally the lower you get the better – the less the gust (but not always). This variability may depend on the type and nature of the turbulence, i.e. mechanical turbulence from trees buildings. Thus the gust characteristics may be airfield specific.
Gusts greater than 15 kt are deemed to be windshear; use special procedures in windshear.
Be aware of how close the gust is to the crosswind limit; give yourself an additional margin. Take particular care with crosswinds on wet runways; check any revised limitations and give yourself a margin.
Approach and landing with less flap may provide a quicker aircraft control response or improved gust response, but do not forget the changes in landing distance.

These are just some of the issues to be considered in a landing decision in gusty conditions. If these are considered collectively they ‘box in’ an operation; the limits of this box should be reflected in SOPs, but these may not include the runway conditions and any changes to landing distance required. Thus crews have to assess the variables on the day, if these require an operation near the edge of the box then reconsiders the alternatives; all conditions requiring operations outside of the box should be diversions.
Any other ‘basics’ or considerations?

Airbus aircraft may have specific differences; see FCOM; also see the briefing notes in these sections - Approach / Landing techniques.

Wing Files- several good references here; in particular see the ‘Performance’ section.

Other information here:- ALAR Additional Resources. (including Spanish and Russian versions).

Gravox, have a look here, there is good information on the 737:http://www.smartcockpit.com/

Thanks for all of your inputs. It's most appreciated. It seems stupid that some guys have come up with there own additives and own variations, I don't know where they get them from. I know I will follow the SOPs.

Cheers

Caution. Never forget that the company SOP's which are generally legally binding, are the work of the latest broom to sweep clean. In other words the chief pilot will often have his own imprimatur on the company ops manual. It is not uncommon for these people to disagree with a manufacturer's FCOM or FCTM and change the facts to suit. For example I have observed former BAC One-Eleven senior management pilots change Boeing manuals to reflect their experiences on the One-Eleven. Suddenly decades of Boeing research and developement is tossed into the rubbish can and One-Eleven flying techniques introduced as purported Boeing published material.

Where possible try and cross-reference company produced information with that of the aircraft manufacturer's FCOM, because it is there in the original FCOM where often the real good gen lies unsullied by egos and personal opinions.

In Pprune, especially on the technical pages, there are some experts too, and cross-reference with their experience and opinions is often useful to build on your own knowledge. By all means cover your backside and career by adhering to the company FCOM, but quietly keep an eye on the manufacturer's advice, whether it be aircraft and engine handling for a particular aircraft or even its avionics and radar systems for which specific information manuals are available from each manufacturer. Not all this information is incorporated in company FCOM's.

I'll keep it simple for you without causing much confusion. 1/2 wind component + all the gust. Max 20kts additive. Flaps 30 recommended in gusty conditions to prevent blow back when flaps 40 at approach speeds in the vicinity of 160kts (max. landing weight). Hope that helps.

Careful, according to the FCTM it is "half the reported steady headwind component plus the full gust increment above the steady wind to the reference wind."

Remembering to bleed off the half the steady HW component approaching touch down. This does not mean in the flare manoeuvre but on final approach. The free stream wind is generally accepted in meteorological manuals as the wind usually above 2000 feet where it considered unaffected by ground friction. Having said that very few operators bleed back the half the steady HW component, preferring to take the excess speed and dissipate it during the landing run - rightly or wrongly.