Autopilot "Bobbing"

So I’ve been frequently having this issue with the autopilot in Infinite Flight. When slowing down to my final approach speed, the autopilot suddenly fails to maintain the given speed and altitude setting and overcorrects way too much leading to a sort of “bobbing”.

For example, yesterday I was doing a flight with the new A350. However when setting full landing flaps and a speed of 140KTS (Which I usually opt for as my final approach speed for airliners in IF as I don’t have an exact vref speed) and an altitude of 3000ft to set myself up for final approach, the speed would frequently fall below 140KTS leading the autopilot to over correct by applying near full throttle. The over correction caused the aircraft to pitch up drastically and accelerate to way above 140KTS. Once this over correction is complete, the autopilot tries to correct the new incorrect altitude and speed but fails to do so. It lowers the throttle and lowers the pitch but then lets the speed fall below 140KTS and the same over correction occurs again.

I don’t know what I’m doing wrong here so if anybody can help me with this I would appreciate it a lot.

Thanks~!

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This does happen, your best bet is to stabilize the aircraft manually then re-enable autopilot. And 140KTS seems a bit low for almost every aircraft.

Have you tried increasing your approach speed at all? As in coming into the cone above 160 knots Indicated Air Speed Flaps 3 then making your way down to roughly 150 knots. It sounds like the over correction is coming into play to prevent a stall.

140 might be a little too slow to maintain 3,000 in an A350, 140 is fine if you’re descending steadily though

I mean I tried 145kts and a little higher, the over correction still occured. Granted this was before I stabilized it manually so maybe I might try this.

I didn’t know 140 was a bit low though. So to make sure I got this, should I try to enter the cone at 160KTS and then descend at 140-145?

Entering the ILS cone between 160 knots and 180 knots being the maximum is good. At touchdown you will be fine at 140 IAS but during the descent and before you flare you may be at 145 IAS. The key is to maintain a good forward speed if you are in level flight. Otherwise if you are flying level with too slow of a speed and you have considerable weight onboard (such as fuel), 140 knots can be difficult to maintain in larger aircraft even with full flaps and positive trim.

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No. 140 knots is one of the higher final approach speeds for aircraft such as 737 and a320

140kts is an appropriate final approach speed when descending, but it would not be an approapriate speed to level off at 3000ft.

You have to disengage speed hold autopilot , control your speed manually , it stops from overcorrecting and pitching up and down, it usually works for me .

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