Understanding altitude etc

[easymo3 0]

Hi guy's I am new to the sim world.

 

I have been using fsx for a little while and what I know about flying in fsx is very limited.

 

I have the pmdg777 and have to say I is just out of this world compared to the stock planes in fsx.

 

I have subscribed to navigraph for the year, currantly on  AIRAC cycle 1507 the  navigraph manager update both pmdg and fs commander

 

Now i can plan the flight using fs commander get the sid and star sorted and loaded into the pmdg data base, i can see the legs ect are all there.

 

I  take off using lnav and vnav, but  can not land the plane, it is all to do with me not understanding what is going on with altitude.

 

I have no idea what to do with regards setting up the altimeter, I press "B" in fsx to reset it but that does no good.

 

Can somebody please explain what I am not doing or should be doing with regard taking off from one airport and then resetting to correct altitude for the landing airport?

 

It is the one thing that I have got really stuck at and it is very frustraiting, I seem to be able to fly the 777 but understanding what is going on with altitude has me stumped.

 

Any input into this matter would be very gratefully recieved.

 

This is my first post, I hope I have got my name in the right place!!

 

Many thanks for taking the time to read this.

Nick.

[scandinavian13 5,192]

 

 

Can somebody please explain what I am not doing or should be doing with regard taking off from one airport and then resetting to correct altitude for the landing airport?

 

Nick,

 

The tutorial that comes with the 777 is more than enough for the questions you have, especially when it comes to getting the plane to do what you want it to do.

 

As far as your altitude and the altimeter, I think you may be confusing concepts here:

 

Your altimeter simply reports how high you are above mean sea level (MSL). In order to accurately report your altitude, your altimeter setting must be changed to match local pressure. If you were standing next to the ocean on a "standard" day (pressure of 29.92 - there are other factors, but we'll ignore them for this discussion), your altimeter being set at 29.92 would indicate nearly zero. If the pressure then increased, you would need to adjust the altimeter to match the pressure change such that it read nearly zero again. In other words, adjusting the altimeter (hitting 'B') simply corrects for pressure changes in the air to make your reported altitude more accurate.

 

In order to climb or descend (change altitudes), then you need to instruct the autopilot to do so. In the case of the VNAV descent, you must give the autopilot "permission" to descend, by changing the MCP altitude lower than your cruise altitude prior to the top of decent (T/D). If you happen to forget doing this until after the T/D, you simply need to press ALT INTV (the middle of the altitude wheel of the MCP) to get the aircraft to descend. More is explained in the tutorial, which I will defer to as it is more detailed, includes pictures, and will teach you a lot more than me writing here (Start Menu > PMDG Simulations > 777 folder > Tutorial)

[Budbud 227]

Hi,

 

First a short explanation on how your altimeter works. It measures the atmospheric pressure to translate it into altitude based on the principle that 1013 hpa (29.92) corresponds to the 0 at sea surface and that the pressure decreases with the altitude.

In a perfect world your altimeter would always indicate the correct altitude. However we are not in a perfect world and the pressure varies with the weather phenomenons (the pressure at sea surface is not always 1013hpa!).

 

To get a correct reading of the altitude on your altimeter, you need to correct the reference of your altimeter which is called the QNH and is given in the ATIS of the airports.

So before takeoff and before landing, you have to set your altimeter to the local QNH.

 

However, above a certain altitude or flight level (clear of terrain and obstruction), you will reset your altimeter to 1013hpa so that all aircrafts have the same altitude reference while enroute and no matter how the pressure varies along your route.

 

Up to what altitude after takeoff and below what altitude before landing?:

You will find two very usefull pieces of information on the airport charts: the TA and the TL.

The transition altitude (TA) is the the altitude above which you will reset your altimeter to 1013hpa after takeoff.

 

The transition level is the flight level below which you will set your altimeter to the local QNH before landing which will allow you to have corrected readings of altitude for your local airport.

[easymo3 0]

Hi scandinavion 13  and many thanks for your reply.

 

I have no problems as far as decending to the airport, it is when I  capture the localiser and then the glide slope

Fmc tells me no autoland, this is because my altutude is not set correctly.

 

I have pressed B to reset, is there a proper time to reset it?

I have followed the tutorial 1 but alot of it has flown me bye!

Maybe time to follow it again.

Hi,

 

First a short explanation on how your altimeter works. It measures the atmospheric pressure to translate it into altitude based on the principle that 1013 hpa (29.92) corresponds to the 0 at sea surface and that the pressure decreases with the altitude.

In a perfect world your altimeter would always indicate the correct altitude. However we are not in a perfect world and the pressure varies with the weather phenomenons (the pressure at sea surface is not always 1013hpa!).

 

To get a correct reading of the altitude on your altimeter, you need to correct the reference of your altimeter which is called the QNH and is given in the ATIS of the airports.

So before takeoff and before landing, you have to set your altimeter to the local QNH.

 

However, above a certain altitude or flight level (clear of terrain and obstruction), you will reset your altimeter to 1013hpa so that all aircrafts have the same altitude reference while enroute and no matter how the pressure varies along your route.

 

Up to what altitude after takeoff and below what altitude before landing?:

You will find two very usefull pieces of information on the airport charts: the TA and the TL.

The transition altitude (TA) is the the altitude above which you will reset your altimeter to 1013hpa after takeoff.

 

The transition level is the flight level below which you will set your altimeter to the local QNH before landing which will allow you to have corrected readings of altitude for your local airport.

Badbud, thanks

I think that is the info I am missing!

I will study what you have posted and try to get my head around it.

Once I have understood and imlimented your post I think I will be landing So thank you for posting that.

[Budbud 227]

I have pressed B to reset, is there a proper time to reset it?

I have followed the tutorial 1 but alot of it has flown me bye!

Maybe time to follow it again.

 

Check what is the Transition level and set your altimeter to the QNH given in the ATIS of your destination airport when you get below that level.

Then double check before your capture the ILS that the QNH has not changed.

Depending at which distance of your airport you press B, you would end up with a wrong altimeter setting.

 

Sorry our posts crossed each other.

Edited June 25, 2015 by Budbud

[scandinavian13 5,192]

 

 

I have followed the tutorial 1 but alot of it has flown me bye!
Maybe time to follow it again.

 

If you don't get it the first time, try it again. Use pause as necessary.

[easymo3 0]

Hi,

 

First a short explanation on how your altimeter works. It measures the atmospheric pressure to translate it into altitude based on the principle that 1013 hpa (29.92) corresponds to the 0 at sea surface and that the pressure decreases with the altitude.

In a perfect world your altimeter would always indicate the correct altitude. However we are not in a perfect world and the pressure varies with the weather phenomenons (the pressure at sea surface is not always 1013hpa!).

 

To get a correct reading of the altitude on your altimeter, you need to correct the reference of your altimeter which is called the QNH and is given in the ATIS of the airports.

So before takeoff and before landing, you have to set your altimeter to the local QNH.

 

However, above a certain altitude or flight level (clear of terrain and obstruction), you will reset your altimeter to 1013hpa so that all aircrafts have the same altitude reference while enroute and no matter how the pressure varies along your route.

 

Up to what altitude after takeoff and below what altitude before landing?:

You will find two very usefull pieces of information on the airport charts: the TA and the TL.

The transition altitude (TA) is the the altitude above which you will reset your altimeter to 1013hpa after takeoff.

 

The transition level is the flight level below which you will set your altimeter to the local QNH before landing which will allow you to have corrected readings of altitude for your local airport.

Many thanks for this explanation Budbud, it is exactly what I was missing.

I have been flying egll-egcc Heathrow-Manchester and after about 15 attempts   tonights flight  is this first time I have had a land3.

So just to clarify   TA we set altimeter to 1013hpa  and TL we set to what ever atis tells us the altimeter is for the landing airport?

EGCC was 29.92 so I did not alter it but if atc said it was 29.98 I would adjust the setting in altimeter to 29.98?

[Budbud 227]

So just to clarify   TA we set altimeter to 1013hpa  and TL we set to what ever atis tells us the altimeter is for the landing airport?

EGCC was 29.92 so I did not alter it but if atc said it was 29.98 I would adjust the setting in altimeter to 29.98?

 

Yes. when descending, check the ATIS to get the local QNH and set your altimeter when you reach the TL.

So above the TRL your altimeter is reset to 29.92/1013 (or STD in the case of the T7, which is the same basically).

If the local QNH was 29.98 at EGCC, you would set your altimeter setting to that value when descending through the TL.

 

And the opposite when you take off, on the ground during your preflight flow you would set your altimeter to the local QNH (e.g.: 29.98) and reset to 29.92/1013 when you climb through the TA.

 

By the way, below the TA, you will fly an altitude (e.g.: 5000ft). Above the TRL you will fly a flight level (e.g.: FL320).

So the TRL is the lowest flight level and the TA is the highest "altitude" with regards to phraseology.

 

The TA is always indicated as a fixed value on the charts while the TRL may be given by the ATC. in that case I usually take a TRL 1000ft above the TA.

 

e.g. at OMDB (Dubai):

TRL 150 (> altimeter STD or 29.92)

TA 13000 (< local QNH)

 

e.g. at EGCC

TRL ATC

TA 5000

 

In the later, if there is no ATC available, to give me the info in fsx, I would probably choose TRL 060 (1000ft above the TA as it is quite common in Europe).