Aircraft datum

[dallas48]

In the center of the HUD is a fixed aircraft datum "W", which shows the position of the aircraft’s longitudinal axis.

 

What is this actually used for?

[MikeMikeJuliet]

When you land or take off for example, you need to know the maximum angle you can pitch the nose up while still on the ground. Otherwise you might hit your tail on the runway. It is also a very handy fixed mark to controlling your attitude when maneuvering extensively, since you might not see your flight path marker all the time.

 

Regards,

MikeMikeJuliet

[dallas48]

Ok, that makes sence to me. Sometime I pull the nose too high areo braking and and scrape my tail feathers.

 

Is there some way you use it for max sustained or instantanious turn? (besides speed, load out, altitude)

 

Thanks for the answers guys.

[Svend_Dellepude]

Approach is flown on AoA in the F-15.

21 units AFAIK on a 3 deg slope.

[strikeeagle]

Shows you where the nose is actually pointed.

[dallas48]

So say Im just about to touch down, 170 knts, 50ft alt, 20 units aoa, a/c datum at 10 deg. fpm on the runway threshold (air brake out, flaps up) how would I determine my glide slope?

Edited October 24, 2016 by dallas48

[P3CFE]

Not that easy to explain,

 

Normally you are instructed and practicing circuits on a specific airfield.

there you are beeing instructed to turn final at a certain distance and altitude.

This gets you on final, at the correct distance and alt, you then see the runway in certain and correct perspective.

 

This,image of the runway, you got to remember to estimate the correct position on glide slope for future approaches, normally 3 to 3.5 degrees ..

This perspective should remain the same during final until flaring.

 

so..if you are getting to low on glideslope, the runway perspective changes into a more compressed image, i.e. the runway-end visually seems to get closer to te beginning of the runway .

 

If you are getting to high on glide the runway perspective changes to a more streched view of the runway, so runway-end seems to get further away from the biginning of the runway.

 

So.. youre goal is to innitially get into the right position on glide (training and instruction), and then keep the perspective on the runway unchanged during the approach until flare.

 

It's fun if you master this..but it takes some exersize.

 

Hope this helps...(Flying is fun)

[MikeMikeJuliet]

Not that easy to explain,

 

Normally you are instructed and practicing circuits on a specific airfield.

there you are beeing instructed to turn final at a certain distance and altitude.

This gets you on final, at the correct distance and alt, you then see the runway in certain and correct perspective.

 

This,image of the runway, you got to remember to estimate the correct position on glide slope for future approaches, normally 3 to 3.5 degrees ..

This perspective should remain the same during final until flaring.

 

so..if you are getting to low on glideslope, the runway perspective changes into a more compressed image, i.e. the runway-end visually seems to get closer to te beginning of the runway .

 

If you are getting to high on glide the runway perspective changes to a more streched view of the runway, so runway-end seems to get further away from the biginning of the runway.

 

So.. youre goal is to innitially get into the right position on glide (training and instruction), and then keep the perspective on the runway unchanged during the approach until flare.

 

It's fun if you master this..but it takes some exersize.

 

Hope this helps...(Flying is fun)

 

I'm sorry, it is not that difficult. 3 things. You need to keep the flight path marker on the runway threshold (1), keep the flight path marker on the 3 degree position in the HUD at the same time (2), and use thrust to maintain ~21 degrees of AOA.

 

I've attached a screeshot where all these are more or less aligned.

 

 

EDIT: If you go too high, you see the runway threshold lower than the -3 mark, if you are lower, you will see the threshold above the -3 degree mark. To get back to the right position place the flight path marker so, that the runway threshold is in between the Flight path marker and the -3 degree mark.

 

 

Regards,

MikeMikeJuliet

Edited October 24, 2016 by MikeMikeJuliet

[P3CFE]

With HUD and FPM its easy..i know, but i was explaining the situation and aircraft types where ther is no HUD available.

A pilot should be able to fly on its primary instruments and this is not a HUD.

 

Greetz

[P3CFE]

Pytagoras is flying with us...Nice :)

 

Great calculaton tricks..

 

Thanks !!

[Xenovia]

i actually never knew what the W on planes were, i thought that it just meant where my landing gears position would be, so the middle arrow looking shape of the W is the front nose gear, and the rear landing gear is represented as the two arrows, pointing down on a W.

[dallas48]

Thank You all for taking the time to explain it to me.

 

 

1. At 50ft you don't care about the glideslope anymore. Below 100-200ft you normally keep the present attitude and at 50ft you are almost starting the flare.

 

2. Approach speed devided by 2 and multiplied by 10 is your 3deg glideslope. In your example: 170/2 = 85 x 10 = 850ft/min.

BTW, if your pitch attitude (what you call a/c datum) is 10deg and the glideslope is 3deg then the actual AoA is 13deg. (not to confuse with units)

 

3. As P3CFE mentioned, you need to be at the correct altitude and distance to be able to fly a 3deg glideslope.

Fortunately this is another easy calculation. Distance x 3 = altitude. E.g. 4NM x 3 = 1200ft.

 

4. Why would you want to land with flaps up? With flaps up your approach speed is higher, pitch attitude is higher and speed control is more difficult.

 

 

 

Thats beautiful, totally get it!

Love learning stuff like that.

 

4. Why would you want to land with flaps up?

 

I kept bouncing on touchdown with them down...... but now I know why.

 

 

Ill bet thats going to make my carrier traps way better too.

 

Thanks again

[proletariat23]

Good info here, much respect to the posters . Total noob been doing heads down instrument landings no problem. Now if I could only AAR.

[milit]

2. Approach speed devided by 2 and multiplied by 10 is your 3deg glideslope. In your example: 170/2 = 85 x 10 = 850ft/min.

 

3. As P3CFE mentioned, you need to be at the correct altitude and distance to be able to fly a 3deg glideslope.

Fortunately this is another easy calculation. Distance x 3 = altitude. E.g. 4NM x 3 = 1200ft.

It doesn't work for metric system... :)