Strong winds on landing at EGNM - management or software incongruity

[MED1473 18]

Hi all, I've recently come across a strange behaviour of fsx/IVAO weather engine/ngx. I was performing a fail op autoland on RWY32 at Leeds with winds from 240 deg at 18kt gusts 28kt, established on final, loc and gs captured and stable, full landing configuration and speed norm. Descending below 2000ft the speed starts to shoot up to about 190kt. Performed a go around and tried the approach again. Same story, fully established, configured and speed about 160kt. Autothrottle on obviously. Again speed below 2000 ft shoots up, tried speedbrakes to no avail, this time autopilot disconnects just above the threshold and I end up wondering how much a new plane is gonna cost. Anybody has any idea? Is this normal behaviour or is it an abnormality o the software.

In any case I would appreciate any advice on speed management when on a glideslope, essentially, how to slow don and manage a landing in strong wind conditions, eg. Speedbrakes, flaps down to 40?

Ps pretty positive is WAS NOT windshear but an established condition and I couldn't get the speed down.

Cheers, matteo capocefalo MED1473

[rocketfs 2]

Hi,

 

Fully configured at a speed of 160kts seems fast to me. What weight did you have?

If the speed goes suddenly up, it can have to do with the wind. Try the same landing without IVAO and no wind.

 

I'm not sure if a lot of operators would let you do an autoland with 28kts gusting crosswind either...

 

Best Regards,

Bert Van Bulck

[MED1473 18]

Hi Bert, no, sorry my mistake but speed was normal, as any other parameter, the trouble started at flaps 30, speed 152kt (Vref+5) fully configured and "stable". You might have a point on the crosswind tho even tho the speed variation, it literally shot up from 160ish (slowing to Vref) to 200ish Kts, seems more like a weird sudden tailwind

MED1473

[rocketfs 2]

Hi Bert, no, sorry my mistake but speed was normal, as any other parameter, the trouble started at flaps 30, speed 152kt (Vref+5) fully configured and "stable". You might have a point on the crosswind tho even tho the speed variation, it literally shot up from 160ish (slowing to Vref) to 200ish Kts, seems more like a weird sudden tailwind

MED1473

 

Hi,

 

I would say a sudden nose-wind. Excessive tailwind would drop your IAS.

Next time you have this, monitor both IAS and Ground Speed. That might tell you something.

 

Bert Van BUlck

[G-CIVA 62]

Hi all, I've recently come across a strange behaviour of fsx/IVAO weather engine/ngx.

 

Both of these WX 'engines' as you call them are notoriously problematic...you'd be better using a third party WX engine like Activesky 2012 - it provides much more stable, accurate & therefore realistic WX input to FSX.

 

I was performing a fail op autoland on RWY32 at Leeds with winds from 240 deg at 18kt gusts 28kt, established on final, loc and gs captured and stable, full landing configuration and speed norm.

 

The crosswind & gust components you have described that existed at the time & under these conditions exceed the Autoland design limitations set by the Aircraft & Autopilot/Autothrottle manufaturers - the characterisitics of which PMDG has faithfuly reproduced within the limitations of FSX. The limitations may vary slightly from operator to operator but are generally ....

 

Headwind 20kts

Crosswind 15kts

Tailwind 10kts

 

So I am not really suprised the approach became unstable...your asking the Autopilot/Autothrottle to cope with a crosswind component varing from 18-28kts including gusts...the autopilot is simply not designed to cope under these conditions & you are asking a little too much of it.

 

Is this normal behaviour or is it an abnormality o the software.

 

I'd say (I am not a RW NG pilot) that its not an abnormality on the aircraft's part.

 

In any case I would appreciate any advice on speed management when on a glideslope, essentially, how to slow don and manage a landing in strong wind conditions, eg. Speedbrakes, flaps down to 40?

 

The NG has a very efficient wing & is a little slippery...it can either 'go down' or slow down' but generally not both together...keep away from the speedbrake beyond flap 5 & get configured early...be in the landing configuration no later than between 5 to 4NM from the RWY &/or 1500ft aal - fly the approach manually with the Autothrottle OFF if visual from this point or from the MDA using the 'stabilised approach' criteria:

 

A stabilised approach is by definition in the NGX FCOM:

At the correct final approach speed or correcting if less than VREF or greater than VREF+20.

Vertical speed is proportional to the current ground speed

V/S is not more than 1000fpm continuously unless required by the published procedure and briefed prior

On profile and in the landing configuration with engine N1 at appropriate thrust settings

 

Normal landing flap settings for the NG are 15, 30 or 40. Consider Flap 15 in very gusty conditions - the higher approach speed will penetrate the windy conditions & avoid the wrong side of the drag curve. You may also add up to 15kts to the computed VREF (normally in increments of 5 kts so VREF +5, +10 or +15) as your 'bugged' approach speed (set on the MCP & visible on the SPD Tape on the PFD) - this will help you to avoid the wrong side of the drag curve during gusty conditions.

 

Although much maligned around these parts the comprehensive documentation that came with the product is a good read - best of luck!