Autoland - Boeing type

[David Rogers]

Hi,

I use PM Boeing type suite, with Kittyhawk 737 model;

I tried an autoland for the first time last evening. All looked good for a 2 channel auto landing (Flare annunciated, etc), but the plane in fact did not flare at all, and slammed into the runway!

I can confirm that the CDU and the cfg file are showing a Flare altitude of 45'.

Any pointers ?

[npbosch]

Do you have?

FD’s on
Both AP’s engaged
Both Navs to same ILS frequency
Both QNH set the same
Approach mode selected

[ak49er]

What Are QNH?

[Peter Nielsen]

What Are QNH?

Finally, i can help for a change instead of asking :p

QNH: Atmospheric Pressure at Mean Sea Level, in Millibars

It is a pressure setting to refer to the barometric setting which will cause the altimeter to read altitude.

The static pressure is defined as the pressure that the atmosphere is producing. You’ve probably heard of high and low pressure, but in aviation you have to be more accurate than that and measure the pressure with digits.
In aviation air pressure is measured in hectopascal, hPa. ICAO has defined a standard atmosphere* in which the pressure at sea level is 1013.25hPa. This is also called ‘standard setting’ or QNE.
Since the air gets thinner with increased altitude, the pressure is reduced. More precisely with 30hPa / 1000feet*. An aircraft altimeter uses this fact by measuring the pressure around the aircraft and translating it to an altitude.

The pressure at sea level is however not static and an altimeter has to compensate for this in order to show the correct altitude. This compensation is done manually by the pilot by setting a reference that is calculated from the present air pressure. There are two commonly used methods for calculating this reference and they are abbreviated; QNH and QFE.

QNH is the actual air pressure reduced to sea level in standard atmosphere*. When setting the correct QNH, the altimeter will show the airfield’s elevation over MSL (see below), providing that the aircraft is standing on the airfield. QNH is the most common setting in civil and private aircrafts.

QFE is the actual air pressure, not reduced to sea level i.e. the air pressure at the airport. When setting the correct QFE, the altimeter will show zero, if the aircraft is standing on the airfield. QFE is rarely used in commercial civil aviation. VFR-traffic sometimes uses QFE and it is common that military aircraft uses QFE instead of QNH.

To be correct, not only the pressure, but also the temperature has to be taken in consideration in order to measure the true altitude. OAT combined with QNH is used to calculate true altitude.

* In standard atmosphere – as defined by ICAO

Pressure at sea level: 1013.25 hPa
Temperature at sea level: +15 degrees Celsius (C)
Decline in temperature: 2 degrees C / 1000 ft
Tropopaus altitude: 11km
Temperature in tropopaus: -56.5 degrees C
Temperature is constant between 11-20km
btw there are more Q's

QFE : Atmospheric Pressure at Aerodrome Elevation, in Millibars
QNE: Atmospheric Setting at Standard Barometric Pressure

in other words if your ATIS advise of a QNH of 1009 and you have yours set at 1013 the end result will be a 120 feet difference which will lead to a not too good landing..;)

More info here..
http://www.vateud-td.org/pilots/1_New%20Pilots.asp
or simply here
http://www.vateud-td.org/

Peter

[David Rogers]

Norbert,

Yes - I had all of the above conditions set correctly for the autoland. The only thing I should mention is that I disconnected the Autothrottle at around 500' ......

Would this prevent the autoland (flare) ?

Thanks,

David

[Peter Nielsen]

Norbert,

Yes - I had all of the above conditions set correctly for the autoland. The only thing I should mention is that I disconnected the Autothrottle at around 500' ......

Would this prevent the autoland (flare) ?

Thanks,

David

Hi David,
yes because by disengaging Auto Throttle you are not longer in Auto Land mode.

Autoland describes a system that fully automates the landing phase of an aircraft's flight, with the crew merely supervising the process

[David Rogers]

Ah... that will be what caused the problem. I disconnected the A/T to retard manually. I will try again and leave the A/T is this time!

Thanks for the help,

David.

[Peter Nielsen]

just out of curiosity,:?:

why use autoland at all, part of the fun of a full setup is to manually fly!:p

i only use Autoland in CAT conditions otherwise i usually hand fly the approach from FL100 to touchdown, only using autothrottle which i also tend to disengage at around 2 to 3 miles from touchdown.
Peter

[Geremy Britton]

Exactly!! I have never flown an autoland because i dont know how. The fun is flying in the bad conditions etc. i use the autopilot until about 900ft then manually land it looking at the gps as i come in if visibility is poor.

geremy

[Trevor Hale]

Ah... that will be what caused the problem. I disconnected the A/T to retard manually. I will try again and leave the A/T is this time!

Thanks for the help,

David.

One more thing!!!!

There is an altitude in the Project magenta ini file that is the flare altitude. Make sure it is set for your aircraft. Otherwise you will flare too early or flare too late. Trial and error, just try to keep the wheels on the ground :)

[Michael Carter]

I can honestly say I've never flown an AL approach!;)

I disengage the Sperry at the start of the STAR or the Clearance Limit depending on the procedure.