Jump to content

Sign in to follow this  
epopchock

Autopilot not holding selected airspeed

Recommended Posts

I am currently in the process of trying to do a flight from Los Angeles-Tahiti on Thomas Ruth's A340-300, and just yesterday discovered that I couldn't get the autopilot to maintain my selected airspeed of 280 knots.  When the Speed Hold switch is engaged, my airspeed doesn't increase or slowly begins to decrease.  I don't know what could be causing this issue, and I tried reducing some of the aircraft's payload, thinking that was the problem, but no such luck.  I have a copy of the autopilot section of the aircraft cfg. file for this aircraft, if anyone needs that: https://1drv.ms/u/s!AuWqP9oV1Utlh7xQ-Euw4V6xNfK0dA?e=Y1cDqw

Share this post


Link to post
Share on other sites

What altitude are you flying at? At the higher flight levels - in excess of 28000 feet then you should be using Mach hold. A340-300 should possibly be around Mach 0.82 at cruise altitude... which may equate to less than 280 knots INDICATED airspeed..:cool:

What do your N1 engine readouts display? If you're at full throttle already then she won't accelerate.. and I've noticed that the Thom Ruth birds seem a little wheezy at high altitudes even though they have enough power to do the job. EDIT - What I mean is that no airliner has very much excess power once it's 7 miles high (unless it's Concorde...)

Edited by HighBypass
  • Like 1
  • Upvote 2

Mark Robinson

"What's it doing now?"

Author of FLIGHT: A near-future short story (ebook available on amazon)

I made the baby cry - A2A Simulations L-049 Constellation

Sky Simulations MD-11 V2.2 Pilot. The best "lite" MD-11 money can buy (well, it's not freeware!)

Share this post


Link to post
Share on other sites

If you disable Speedhold , and give Full Throttle, does the aircraft then reaches (or exceeds) 280 Knots in the same flight conditions ??

If so:
In the aircraft.cfg, raise the value of 

autothrottle_max_rpm = 92

Try 100 - 110 or so.

Rob        
 

 

 

 

 

  • Upvote 1

Share this post


Link to post
Share on other sites

Hey, guys.  I think you gave me some pretty good suggestions, I will try rcbarend's suggestion and see if it helps.

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Tom Allensworth,
    Founder of AVSIM Online


  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
  • Donation Goals

    AVSIM's 2020 Fundraising Goal

    Donate to our annual general fundraising goal. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.


    28%
    $7,170.00 of $25,000.00 Donate Now
×
×
  • Create New...