Descend Wind vs TOD

[JG69 0]

Good evening

 

I believe there might be a bug in MCDU, when recalculating TOD due to descend wind.

P3D v4.5.13

A320 professional v. 1.3.0.3

 

Let´s create a scenery:

- aircraft at ground. No need to take off.

- No weather engine. Clear sky selected at P3D. (it doesn´t matter, we are no going to fly)

- a complete File Plane filled, including, route, runway for departure, SID, STAR and arrival runway. No discontinuity, from take off to land.

- High FL, let´s say FL390, for a better evidence of the problem.

- It is better to have a STAR with few turns (better none) and few constraints, in order to have a maximum Idle descent during the flight. We can manually  set a constraint at a way point close to FL100, and clear all other constraints above. This way we will have a descend idle path from FL390 to FL100, basically in a straight line.

- ZFW, fuel and flaps selected at INIT page.

- With the information above, MCDU with calculate all data of the flight and  display de TOD  with a white arrow at ND an indicate it at MCDU F-PLN page.

 

Everything is fine till this moment.

 

Now let´s manually insert a descend wind at MCDU (no use of uplink, nor wind request). We will start inserting a 100Knt head wind, at FL340. As soon as this is inserted, TOD is recalculated and moved forward about 20 miles. That´s perfect!

Now we are going to to clear the descend wind and  TOD return to original position. Perfect!

Now we are going to insert a tail wind of 100Knt at FL340, and what happens is that TOD moves forward, as if a head wind was inserted!!!!!!   It should have moved backwards!

Now we are going to insert a crosswind, of the same intensity, and TOD remains at the same position, as in the head wind and tail wind.

Now we are going to reduce the intensity of the head wind to 50Knts. TOD is reduced half way, which looks fine.

 

Conclusion:

MCDU calculation of TOD is not taking account the direction of the wind at descend page, only the intensity, and assuming it as a head wind, which is completely wrong.

 

Best regards

 

Jose

 

 

[masterhawk 799]

We will have look into this, if we can confirm that issue.