Me 262 don`t reach the indicated speed in waypoint

[GOA_Walter_Nowotny]

Hi pilots!

I'am developing my last mission for  a new campaign in 262, but again some troubles with the 262. This time I tried to solve it, but can't:

 

-The planes start the mission in the air, at 4000m.

- Group o 5 262 in "V" formation

- First waypoint, at 4000m and set 600 kph  and so on maintaining height and speed.

 

But all the planes fly at less 370 kph all the trip with flaps down.

Any idea why this?

 

Thank you!

Salutes