Using the heading bug on a HSI?

[machlimter99]

Seems a silly question, but what is the use of the heading bug on the HSI?? Assume that you dont want to use it for the heading; which other uses can it have??

[mad_jock]

Make sure your pointing at the correct runway.

When you enter the circuit set the heading bug to the runway. ie runway 16 set it to 160. Then if you report finals and the bug isn't within +- 20 degs of your heading you know you have lined up on the wrong one.

[jabberwok]

What has triggered the question?
It's a heading bug - to fly headings. Other uses are to set to runway QDM so you don't land on the wrong one, ILS course so you get a nice intercept angle and presetting a fixed course deviation - but these are all still headings.
Is it something else that has prompted the question?

[FormationFlyer]

In some aicraft fitted with autopilot that 'silly' (personally I think they are best since cut-up flour+egg+water based products!) heading bug controls the heading of the autopilot.

[FlyingForFun]

One student of mine who was struggling with PFLs devised a system whereby, whilst slowing the aircraft down, he would set his heading bug to the wind direction as he remembered it from the take-off. He then used this to help him plan his arrival into his selected field. It's not something which I'd normally use a heading bug for, but I couldn't think of a good reason why he shouldn't do this.

Also, the question specifically asked about the HSI, but if you're not lucky enough to have all that equipment and you're navigating using an RBI, I find it more intuitive to have the heading bug set to the track, rather than the heading, for NDB tracking, because you can then visually cross-check the heading bug against the head or the tail of the needle. (Only works if you're not flying on the auto-pilot, of course, and it's not necessary if you've got an RMI.)

FFF
------------------

[rotorfossil]

It can be handy on cross country legs to put the wind on the heading bug and set the heading on the needle as it gives an idea of expected drift. Also handy for working out diversion headings. Put your estimated track on the needle, drop an imaginary line down fromj the bug to a right angle from the track and this gives you the proportion of the max drift to apply to the track.
As mentioned before, when arriving at at an airfield, put the needle on the R/W heading which then gives a useful pictorial picture of which is the correct R/W and again an indication of the likely drift on the D/W leg and crosswind component on the R/W.

[FormationFlyer]

Its also an invaluable aid for applying 'self-control' of heading changes when flying ILS approaches - ala OATS training.

[FlyingForFun]

Very good point, FF - I was taught that, too, and teach it to my IMC students. In fact, I remember finding it extremely difficult to fly an ILS the first time I ever tried it in an aicraft without a heading bug!

FFF
------------

[FormationFlyer]

It is, Ive been doing IMC refresher work with a few pilots recently and the lack of heading bug to help certainly calls for a lot of discipline - not a problem if you are used to heading bugs and were taught by OATS or the like - so you are used to flying nominated headings on the ILS. It certainly helps avoid random heading changes or worse still chasing the needles - which should never be done.

[Farmer 1]

If you have a nav coupler, set the bug on the heading. Then, if the coupler drops out or loses reference, or the NHP starts pressing buttons, it's a simple job to get the aircraft back on heading.

[A and C]

The heading bug drives the roll comand bar on the flight director so you had better get into the habit of seting it to the heading that you want to fly because when you get to fly a bigger aircraft you wll be using the FD most of the time.

[Send Clowns]

I am at a loss as to why anyone would use a heading bug for anything other than current or anticipated heading. It is so helpful for this, improves flying (especially instrument flying) so much that I cannot see how it would eve be available for other tasks!