Nominal width?? A320

[hborderas]

Hi everybody here is a question concerning the FCOM3 limitations section for the A320.
The manual says the minimum runway width is "45 meters nominal". What exactly does airbus means by "nominal"
Thanks in advance for everybody's help

[saman]

I cannot help you with the exact definition of 'nominal' but I would guess that it's the tarmac/concrete width that can accept a wheel running on it and would not include any non load-bearing edging such as gravel.

But with an increased Vmc (minimum control speed), to provide for greater longitudinal control, the A320 can operate off runways down to 30m wide. Obviously the higher Vmc can lengthen field length requirements.

Have a happy day.

saman

[waren9]

I think it refers to the requirement for regulatory authority approval widths less than 45m

Nominally 45m, however here in Australia CASA have given authority for atleast 1 A320 operator to operate into/out of 30m wide RWY's.

[john_tullamarine]

Main difference in Oz (unless things have changed in recent years) is that the aircraft has to demonstrate by flight test its compatibility with the reduced width runway operation.

[hborderas]

Thank you all for your help :ok:

[Big Bad D]

ICAO Annex 14 recommends certified aircraft performance for a 45 metre wide runway. This is what Airbus considers to be "nominal".

Subject to the authorisation of their appropriate regulatory authorities, an operator may be able to operate down to 30 metre runway widths. This is "optional" and applies flight manual (+ FCOM) performance limitation changes based on Airbus flight test and certification.

[Wonder Boy]

The aerospace definition of nominal is: 'within acceptable limits'

[OverRun]

I think that Wonder Boy has got the right definition. Nominal covers those slight imperfections that go on in the real world. We once built a 500m runway extension that was crooked - not aligned to the existing runway and very slightly angled [and I still have no idea quite what we did wrong]. It took some creative linemarking and a bit of cosmetic bitumen edging to cover it up. That runway is (nominally) 45m wide.

[compressor stall]

Yes, overrun, that may be one definition of nominal, but the fact remains that by paying Mr Airbus some extra $, and getting the approval from your regulatory authority the A320 family can operate to 30m wide runways.

[issi noho]

just for fun, if you sent a child out to 23L at MAN to measure the width of the runway, they'd probably tell you its 60m wide. If he/she was a smart kid they'd put in brackets that nominally it 45 m wide and the extra is the shoulders either side. they might tell you the starter extension is 30m wide but some idiot has disguised it in 60 m of concrete to fool you.

either way they'd probably spend all lunch time telling their mates about the crap assignment they'd been given.

[Bigmosquito]

More questions...

ICAO annex 14 gives the RWY width recommendation with an aerodrome reference code. The intent is to provide a simple method for interrelating the numerous specifications concerning the characteristics of aerodromes so as to provide a series of aerodrome facilities that are suitable for the aeroplanes that are intended to operate at the aerodrome.

The aerodrome reference code has a code number and letter (i.e. 4C).
4 - Aeroplane reference field length 1800 m or more.
C - Wing span 24 m up to but not including 36 m, or outer main gear wheel span 6 m up to but not including 9 m. (The code letter shall be determined by selecting the code letter which correspond to the greatest wing span, or the greatest outer main gear wheel span, whichever gives the more demanding code letter of the aeroplane for which the facility is intended).

With the code letter you then enter the tabulation specified in annex 14, 3.1.10.

4C = 45 m in this example.

The interesting bit of the annex 14. It says, as of 27 november 2003, States shall certify aerodromes used for International operations in accordance with the specifications contained in this annex as well as other relevant ICAO specifications through an appropriate regulatory framework.

What about non international runways so to speak?

Also FAA AC 150/5300-13, Airport design gives something slightly different.
It refers to an Airplane Design Group (ADG) from I to VI and 3 RWY WIDTH tables depending on approach speed category and visibility.

So you could fall in 45 m rwy width based on ICAO recommendation and 30 m based on FAA AC 150/5300-13 for the same aeroplane if operating into the USA.

Another concern is what about cross wind limitation? Do we take the crosswind from the AFM in both cases or not?

I checked my AFM and there is no LIM concerning RWY width...

Interesting enough, as I work for an AOC operator, our Part B refers to a LIM of 23 m rwy width?????? Where did they get this from, I have no idea...
Can a Part B be less limiting from ICAO annex 14 and/or FAA AC 1500/5300-13 without any limitation in the AFM?
Our airplane would fall in the 4C category if following ICAO recommendation.
This must be a mistake from our side...

Complicated!... Grrrr!...

Bigmosquito.

[john_tullamarine]

I checked my AFM and there is no LIM concerning RWY width...

Ah .. you noticed.

The problem is one of philosophy.

Most jurisdictions apply the ICAO geometric "limits" without consideration to a specific Type's capability to operate safely on a given runway width.

Many years ago there was a recommendation to look at demonstrated capability and, as far as I am aware, only Australia took that up (back in CJF's time in the CASA - or whatever the name was that week - FT chair).

The boys ran some local airline sim tests and it became very clear, very quickly, that centreline tracking was a bit tenuous with crosswind in critical conditions (read .. "down near Vmcg").

As a consequence, Australia introduced a requirement that concessions against the basic ICAO practice would require demonstration of capability and, for my sins, I was involved with several such of the early exercises. If the aircraft couldn't handle the heat in the kitchen, either the concession wasn't granted or the min speed schedule was limited artificially to make the directional control problems go away.

End result (from watching various aircraft ballet movements through a high magnification video located on the upwind end threshold centreline) was that I became a staunch believer .. which is why I get involved in discussions on (certification) Vmcg and crosswind .. there is nothing slow and progressive about directional loss of control on the ground with a too-low speed schedule .. aircraft exits stage right with an alacrity sufficient to take away one's breath.

our Part B refers to a LIM of 23 m rwy width?????? Where did they get this from, I have no idea...

While not speaking to the specifics of your case, one could opine that there is quite a bit of FITWWAG-based technological decision making involved when it comes to runway width limits and concessions .. a bit like the real olden days when the first rule books were being developed .. the regulators needed some rules (guidance) so they made it up on the run until hard data proved a need to change the wordiology.

[Bigmosquito]

Well at least, you guys ran some tests...

Mmmh! Still wonder about this 23 m. With an airplane with a wingspan of nearly 30 m. Still think it is pushing a bit too far without extra precaution like crosswind, runway conditions, back tracking, etc...

But thanks for the feedback, excellent stuff...

BM.