Author Topic: PMDG 747-8i/F  (Read 1640 times)

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Offline Adrian Chitan

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PMDG 747-8i/F
« on: November 09, 2013, 10:55:48 PM »
Hello, hello!

I have recently bought PMDG's 747-400x and its' -8 expansion. After the normal grinding (reading the manuals and testing it) I commenced into online/VA flying. First flight: Johannesburgh to Bucharest (~5000 NMs). After a normal take off and climb to the first step (FL320) I relaxed and started a movie on my other monitor (the only way to fly). But suddenly, over Zimbabwe, bad weather came with turbulence and the bird started to loose speed and eventually descended to maintain a flyable speed. Luckily, I was expecting this from the 747 because I read a similar behaviour on other forums. So I stopped 2 of my 3 packs so they won't impede on the engines efficiency, stopped anti ice, changed the thrust profile to continous (CONT) in the FMC and set the ignition to continuous, disengaged A/T and applied full throttle (those were all the steps recommended on the forums - though if you have to take them all, than you have a problem). Anyway, the plane started gaining airspeed and I got back to FL320.

A few hundred miles up, more bad weather. This time I was inspired to take an offset to my flight plan so that I would avoid the turbulence (I use ActiveSky as my "weather radar"). But still the turbulence happened (not enough offset) and the plane started loosing speed and altitude. I redid all the things mentioned above but to no avail (though it stopped the deceleration to a certain degree). I lost about 16000 feet this way. Of course, this screwed up my fuel calculation and I was suddenly in a INSUFFICIENT FUEL situation. But the most important thing is that the plane wouldn't climb any more. With it getting lighter I expected to get up in no time. But NOOOOO!
It seemed like the 747 was heavily under powered. With no warning lights whatsoever.

The only explanation I though about was that the combination of relatively heavy plane (300 pax) with the high temperature over central Africa (about -6 C at FL320) made the engines so inefficient that they couldn't maintain normal cruise speed.

I finally got back up (after about 2 hours of flying low). I don't know if that is normal or I am doing something wrong.

P.S. The fuel quantity was correctly calculated. I use different C++ programs made by me, following what PMDG say in the pdfs that come with these simulators.

So, any thoughts?

Offline Dan R.

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Re: PMDG 747-8i/F
« Reply #1 on: November 09, 2013, 11:57:10 PM »
Este normal sa nu mai traga daca la fl320 sa ai temp ridicata (putin aer care se mai si dilata). Am avut aceiasi problema ca si tine cu temp aberanta la fl300+....am participat la un event si la fl350 aveam +18C, avionul era aproape de stal si motoarele in "blana", ctr`ul imi atragea atentia sa maraesc viteza. I-am cerut sa-mi dea fl mai mic ca nu am cum sa maresc viteza cu temp aia....

Sunt curios daca in realitate se poate intampla fenomene de genul asta la altitudini mari ? La munte stiu ca se mai intampla sa fie inversiune termica !


Offline Adrian Chitan

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Re: PMDG 747-8i/F
« Reply #2 on: November 10, 2013, 06:03:21 AM »
Da, deci asta era. Dar e destul de ciudat cand ti se intampla prima data.

Deasupra muntilor e termostatul mai sus, deci intotdeauna vei avea modificare de gradient deasupra lor (dar cu cat mai sus cu atat mai slab efectul si depinde si de anotimp). In orice caz, Africa frige. Nu stiu cum respira oamenii aia acolo...  ;D.
Nu prevad sa se mai intample asa ceva in Europa (cel putin nu in sezonul rece).

Multumesc pentru raspuns Dan. Scuze pentru engleza, am crezut ca asa trebuie.

O zi buna,
Adrian

P.S. Inversiune de temperatura (la propriu, negativul devine pozitiv) poate sa iti dea si weather engine-ul de la FSInn. Asa am citit pe forumuri: la peste FL240 poate sa-ti transforme -23 C in +23 C si deodata avionul o ia razna (normal). Eu folosesc ActiveSky2012 asa ca nu am vazut problema, dar cica ar fi.
« Last Edit: November 10, 2013, 06:06:21 AM by Adrian Chitan »

Offline Dan R.

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Re: PMDG 747-8i/F
« Reply #3 on: November 11, 2013, 12:42:23 AM »
Nu stiu cum respira oamenii aia acolo...  ;D.

off topic....cei din africa de nord au nasul "lung" cu nari mari alungite iar cei din africa neagra au nasul lat cu nari mari rotunde....design special creat sa poti sa inspiri o cantitate cat mai mare de aer cald... ;)

 

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