Wet landing distance private operations

[chr]

Hi everyone

I know that there was a lot of discussions about this but when I started to read all of those posts I finally get lost. I have quick short question to confirm my way of thinking

JET LANDING ON DRY RUNWAY :

private - I can legally go to airfield with LDA available the same as unfactored from aircraft manual (It is not a good idea I know about it but let's put this aside for a moment)

commercial - LDA available must be at least as unfactored landing distance from manual multiplied by 1.67

JET LANDING ON WET RUNWAY :

commercial - factored dry distance must be multiplied by 1.15

private - here I have a problem - manual says that on wet you must first determine factored landing distance and than multiply it by 1.15 but this is required for commercial and what about private ?

Thanks for clarify

[debiassi]

If you want to increase your landing distance parameters, better to use a runway analysis service provider.
At least then if you get ramp checked, you can legally show what figures you used to determine your required landing distance.

Remember however that EASA compliance for non commercial ops is only just around the corner.

[Miles Magister]

CHR

Why do you say that using FM landing distances is not a good idea? They are perfectly fine to use, that is why they are published. When the aircraft is test flown they measure the distances used and factor them for the average pilot in an average aircraft on the average day. If you come over the threshold at 50' or less at Vref with the pwr at idle, like you should on every landing, the distances are more than adequate.

The CAT factors are to cater for people landing beyond the ILS and being too fast.

In the good old days there was a factor to use for your destination and much lower factors for your alternates based on the fact that pilots could become complacent at regular destinations but when they divert they would be concentrating and flying more accurately.

The book figures are perfectly good if you fly accurately.

But to answer your original question you must use your book figures but check the text about whether the figures are already factored, as many are.

MM

[His dudeness]

Why do you say that using FM landing distances is not a good idea?

Where exactly did he say this ?

[Empty Cruise]

@ Miles: "...measure the distances used and factor them for the average pilot in an average aircraft on the average day."

You have a FAR25 reference for that?

States that techniques used must be consistent with 'average pilot' skills - but am willing to eat my last hat if there is any factoring involved. What you see is a factory test pilot simulating degraded skill consistent with an average pilot - but there is no 'factoring fat' for you. Using their 'average skill mode', the test team reliably reproduced stopping the aircraft in the stated distance - no more, and certainly no less.

Most pilots I have observed trying to match the ALD come close - but few meet the numbers.

[His dudeness]

From CS25:


(4) The landing must be made without excessive vertical acceleration, tendency to bounce, nose over or ground loop.
[Amdt. No.:25/3]

(5) The landings may not exceptional piloting skill or alertness.



I´m aware of the fact that 4 might - in some cases - contradict 5. How "they" do that in real life should a test pilot be able to answer.
AFAIK - FWIW - the landing field dist tests are done with brakes and tires worn to the limit.

Although not really part of this discussion, some dudes are not aware that Vref might not be VSO x 1,3 on their type. Some airplane use VSO x 1,23 these days. (E.G. Citation Sovereign) The lesser margin one can will feel in X-winds and or steeper approaches...running out of elevator before touching down happens on the Sov if you´re not careful...

Back to CHR:

manual says WHICH manual ? If it is the manual of the airplane (AFM) then you determine what factor you need to use (1,67 as a comm operator or 1.0 for private ops) and then you factor that with 1,15 - which equals 1,92 for the commercial dudes.

Some non commercial operators use factors such as 1,25 for dry and 1,44 for wet runways (thats what we do).

[cambioso]

That must mean that we non-commercial pilots are deemed more skilled and (therefore) much safer than our commercial colleagues then eh???

Tin helmet donned and ready.................................

Jez.

[safetypee]

chr, the commercial factors 1.67/1.92 are requirements for dispatch and are based on AFM distances. The unfactored AFM distances are not realistically achievable in operation.

EASA requires an assessment of the ‘conditions’ before landing so that the expected distance will be safe (EU OPS1.400). Some operators use the fully factored AFM distances, updated for actual arrival conditions; this should provide an equivalent level of safety as for dispatch.
Some, most, manufacturers provide advisory landing data (QRH/FCOM), which may be based on the unfactored AFM distance or similar calculations. These are unlikely to be the same as the AFM – 1000ft touchdown point, use of reverse, etc, but the unfactored distances may be achievable in operation (emergency use), but the assumptions in the calculations should be carefully studied.
EU OPS requires a minimum additive of 15% above distance calculated – as factored and increased by EU OPS 1.515, 1.520. These distances represent a more realistic value for pilots to achieve with a safety margin, however as noted in FAA SAFO15009 these distances may still be insufficient in some wet conditions.

Although private operations may not be governed by the same regulations as commercial, they will at some point be answerable to a requirement to operate safely. Thus it might be judged that the use of unfactored distances would not meet the minimum safety requirements in aviation.

Book figures are fine if you understand the basis of the book, the factors, the safety margins, and the assumptions made about flight technique (as per #3).
Unfortunately the book doesn’t know when the pilot is going to have a bad day, or the tailwind is stronger than reported or the runway more slippery, … ….

Managing Threats and Errors During Approach and Landing (www.skybrary.aero/bookshelf/content/bookDetails.php?bookId=874)

[His dudeness]

The unfactored AFM distances are not realistically achievable in operation.

Sorry, that is bollocks...

[Astra driver]

When we land our Gulfstream G650 empty at our home base in Burbank CA, we often like to make the C6 turn off direct into our ramp; if we cross the threshold on glide at 50ft and REF (as opposed to the normal REF + 5) landing on the 1,000 ft markers we can make the turn off which is approximately 3,300 ft from the threshold if we use max reverse and moderate braking.

The AFM says we need approx 2,800 ft unfactored to accomplish this. Now ask yourself this; would you really want to land on a runway equal to the numbers published in the AFM with no margin?

[safetypee]

H d. #9, the internet enables a range of opinions, but without justification they are of little value in a professional forum.

The certification requirements are in CS 25; guidance as to how these regulations can be met is given in advisory materials, e.g. AC 25-7B.
There are several acceptable methods for determining landing distance, which can consider the landing as separate segments. The air distance from 50 ft to touchdown, a transition distance, and the brakes on to stopping distance. These segments are 'stitched' together (as they are often tested in isolation) to form an acceptable model of the aircraft performance; this is the basis of the manufacturers' data (AFM).

An operational view of this is given in AIC 14/2006 Landing performance of large transport aeroplanes (www.ead.eurocontrol.int/eadbasic/pamslight-5FDD7B3D273F647C62B22353EC3D55D9/7FE5QZZF3FXUS/EN/AIC/P/014-2006/EG_Circ_2006_P_014_en_2006-02-02.pdf) –
‘This gross distance should be regarded as a theoretical minimum, consistent achievement of which requires a high level of pilot skill under favourable conditions, and concluding in a level of deceleration that would normally be considered excessive from the passenger comfort point of view’.

The AIC continues with practical advice for operators, noting that although it is still current it relates to JAR-OPS. One contentious issue is the allowable speed margin at the threshold, which may only apply if all other variables are at the datum value.
Note and heed the concluding remarks in the summary.

Guidance for the performance for light aircraft (perhaps more related to a private operation) is in AIC 127/2006. (www.ead.eurocontrol.int/eadbasic/pamslight-5FDD7B3D273F647C62B22353EC3D55D9/7FE5QZZF3FXUS/EN/AIC/P/127-2006/EG_Circ_2006_P_127_en_2006-12-07.pdf )
Paras 7 - 7.7 ‘Safety Factors: it is recommended that the public transport factor should be applied for all flights. For landing, this factor is x 1.43’ (propeller aircraft factor?)
Also see ANNEX - landing and notes 1 - 3.
.

[733driver]

I think you are both right. The key may be "large transport aeroplanes". It has been my (unscientific) experience that smaller GA jets which are likely to be operated privately, possibly even single pilot, achieve unfactored landing distances relatively easily if flown right. On the 737 it was not that easy and required everything to be done just right: virtually no flare, exactly on speed, max braking etc.

I believe (but cannot prove it) that most GA manufacturers add a little fudge factor (probably by telling their test pilots not to try "too hard"), in order to protect against future runway overruns by private operators, including single pilot, owner-flown ops.

[wanabee777]

We almost went off the end of runway 22 at KBTR one rainy night in a 727.

Why? Because the Captain forgot to deploy the spoilers.

If the F/O hadn't reacted as quickly as he did by reaching around and grabbing the spoiler handle, we would have most certainly gone off.

Brake and tire (tyre) condition not withstanding, the biggest factor affecting deceleration rates for most aircraft is the weight on the wheels. The more weight on the wheels, the greater the coefficient of friction between the tires (tyres) and the pavement given the effectiveness of the brake and anti-skid systems.

Some light aircraft owners, who have "manual" flaps, will "dump" the flaps on touchdown to rid the wing of as much lift as possible thus putting more weight on the wheels.

[His dudeness]

safetypee, it does (the inet) and I could bringt you umpteen examples of landings I made that were at least very close to these numbers. The internet in turn is a place where I could be anything from being an experienced pilot to an armchair dude...

I will - on your request - narrow it down:

that is bollocks for the types I have flown.

Those were a lot of Cessnas (C500-550-560 in all variants but the Encore+, C525 in all variants nut the CJ3+ & CJ4, C650-III & VIII, C680), Kingairs (mostly B200s) and the Challenger 300….(most of these are not true FAR25s types but the 650, 680 and the 300 are)

These aircraft are remarkably easy to fly, the proof (IF you believe this post/poster) is, that I haven't had an accident - cause I´m an average pilot at best.

There are few overruns to start with in this category, but the ones you find in the news/acc reports have one thing in common: very bad judgement on the pilot side. Recently: Blackbushe / Phenom 300. Putting down half down a short runway with overspeed gets you in trouble. If you don´t understand that, then... None that I have seen was down to mechanical failures etc. One could argue that because of the relative low numbers required, almost every time the airplane has more than even the factored distances available. True. However, I have done hundreds of landings on a runway that has a very limited lenght (LDA 3323ft) and has a bad obstacle situation on top of it. (prevents you put the 50ft point before the THR - in fact you need to follow a 4° PAPI in order not to take out big lorries on the elevated 6 - lane road right in front of the THR 27) None was even close to use significant more than the unfactored distance. Now, I use reverse thrust, but as the reversers are so slow to open on the C680, we hardly get any real effect from it. I landed B200s there CJs, CJ2s CJ3s, the C680 and the Challenger 300.

Of the 1500ish landings our C680 has by now, roughly 450 were made there.

[EatMyShorts!]

My (commercial) outfit also uses the factors 1.25 (dry) and 1.4375 (wet) when we operate "private". It just gives us some room to play with, we cannot make perfect landings as published in our books.

[deefer dog]

I have never had a problem achieving un-factored AFM quoted landing distances in either small, med or large cabin biz jets.

I'm no magician or test pilot either - there's not much skill needed to cross threshold at Vref, at correct height, plonk it on and push with yer feet!

[Above The Clouds]

The answer is found in the title 'private operations' do what you want.

[Piltdown Man]

...we are of course assuming your manufacturer actually provides ALD WET figures. The only ALD WET figures provided by Embraer (E190/175) are for Abnormal and Emergency operations. Contaminated data also exists. But you have to stick your finger in the air for 'normal' wet operations. I add 20% to DRY and it appears to work.

But whatever the numbers are, you must always ask yourself if you are being very wise operating into a place where the LDA is approaching the LDR, wet or dry.

PM

[His dudeness]

if you are being very wise operating into a place where the LDA is approaching the LDR

Pays my bills actually. (Homebase).

I´m part of an initiative to get bigger runway build a few clicks away on an unused US AAF - currently impossible in Germany with all the green beans and lefties in politics. They want to shut our airfield down and move us to a nearby VFR field that is a tad longer. If you ask me wether I´d like to be based on a VFR airfield with better margins or my current filed with a LOC/DME & RNAV/GPS, I`ll stay where I´m right now.

[wanabee777]

Not trying to be picky, but if one looks at the friction formula, the friction force will increase with more weight on wheels but not the coefficient of friction.

Fr = μN

where:

Fr is the resistive force of friction
μ is the coefficient of friction for the two surfaces (Greek letter "mu")
N is the normal or perpendicular force pushing the two objects together
μN is μ times N

I don't consider you being picky at all.

I stand corrected.

Friction force is the appropriate term which applies here.

Thanks for setting me straight!!