Airspeed (IAS) Bugs

[Rajah 1]

Hi there!What is the use of the IAS speed bugs and what effect does it have during take off and landing or is it just to remember the speed (V1 -VR - V2 Vyse) that has to be flown?

[Chock 17,769]

You are correct.Typically the old fashioned ones that you move manually around the ASI bezel are just visual aids to help you recall what your correct speeds are with a quick glance. Ones that appear automatically on speed tapes are calculated based on your weights and temperature inputs into the FMC, although you can override that and put your own in manually. You can set them to anything you like if it helps you, but V1, Vr, V2 and Vref are the most common things they would be set to and would be part of the procedures for take offs and landings in some types. You can also find some aircraft have a selector for other bug settings, such as N rotation and things like that.Al

[Rajah 1]

You are correct.Typically the old fashioned ones that you move manually around the ASI bezel are just visual aids to help you recall what your correct speeds are with a quick glance. Ones that appear automatically on speed tapes are calculated based on your weights and temperature inputs into the FMC, although you can override that and put your own in manually. You can set them to anything you like if it helps you, but V1, Vr, V2 and Vref are the most common things they would be set to and would be part of the procedures for take offs and landings in some types. You can also find some aircraft have a selector for other bug settings, such as N rotation and things like that.Al

Thanks Al. Very clear now!