Autopilot after takeoff problem

[Enzzo 1]

Hi friends.

Please help me with the following problem. After takeoff, when the autopilot engaged, instead of continuing to set the pitch gradually decreases until the negative values ​​of VS. Only then, if AP was not DISCONNECT due to strong deviation from the Flight Path displaed FD, aircraft leveled. Fly it for a long time and can not understand the reasons for this behavior. Screens cause now I can not, but the rise was producing as follows (I use FS2Crew Voice Pack and same commands performs by FO):

- Activate the FD in the TOGA button on the lever of power

- Armed HDG and Alt Sel autopilot panel (height adjuster more acceleration height)

- Flaps 9, lighting, etc.

- After takeoff, landing gear up

- Trims for FD

- If there is no need for speed dial, follow the FD; if there is - keep pitch just over Vyse to a safe altitude and then accelerates.

Autopilot engaged, as appropriate at any stage of take-off, but not below 400 'AGL.

The last two days leafed through AOM, but due to the large volume and poor knowledge of the language could something and overlook ...

Thank you for any help .

[ckyliu 1,749]

You need to select a pitch mode when engaging the autopilot, such as:

• IAS adjusts pitch to maintain IAS (the target is set whenever you engage IAS mode. Use the wheel on the autopilot to adjust the target)
• VS adjusts pitch to maintain Vertical Speed (the target is set whenever you engage VS mode. Use the wheel on the autopilot to adjust the target)
• ALT holds your present altitude

ALT SEL is not a pitch mode, it engages ALT hold when you reach the target altitude.

[Enzzo 1]

Ok, I'll try it.
But only if I remember well, I tried to engage a vertical mode BEFORE to turn on the autopilot and it did not help ...

Thank you.

[ckyliu 1,749]

Just remember the target VS/IAS is set when your press their buttons, so if you press them before takeoff the target will be set to 0 kts or 0 fpm!

[downscc 1,327]

My usual practice is to engage AP in V/S mode above 400 AGL, about 800 fpm which even when heavy will allow the aircraft to accelerate. Make sure you do accelerate.  Then at 170 KIAS I switch from V/S to IAS and hold the recommended climb speed of 170 KIAS until altitude capture.  Only use V/S in climbs with caution, it has the capability of decreasing your airspeed if the rate is too high for weight and atmospheric conditions.