Precision Simulator update 10.173 (24 February 2024) is now available.
Navburo update 13 (23 November 2022) is now available.
NG FMC and More is released.

Main Menu

Airspeed bugs on standby altimeter

Started by Will, Tue, 7 Oct 2014 02:42

Jeroen Hoppenbrouwers

My company always lets the Digital Deviation Transducer take care of these things. Old school...


Quote from: Will on Tue,  7 Nov 2017 03:11
I took a ride in a UAL 737 sim a while back, with a UAL instructor. He said, very authoritatively, "United always uses a five-bug takeoff." I've always wondered what really meant. He didn't explain.

One of these days I want to say to some students in a sim "we always use a 57-bug takeoff. We bug 30 knots, then every 10 knots from 30 until V1, then V1, VR, V2-5, V2-3, V2, V2+3, V2+5, every flap retraction speed minus 5 and minus 3, plus Vmax minus 5, 10, and 15, and Vmin plus 5, 10, and 15, and Vso plus and minus 10, 5, and 3, and Vs1 plus and minus several speeds, Vno, and Vno-no, and Vno-no-no, and randomly 137 knots. And 287 knots. Plus the V speed closest to the serial number of the #2 engine."

I think this is funny because according to me, the thickness of a single bug is about 5 knots (for an airbus a340) from my point of view....

It is like IMHO standby instruments Was not designed to be used in real... it was more like a regulatory requirement




My standby ASI has so many bugs, the bugs have bugs!

In other news - the flight crew are so busy setting speed bugs, they forget to fly the aircraft...


Ah - that's what 'children of the magenta' do when forced to fly a manual approach on the standby instruments - set speed bugs!



Don't forget they're busy referencing the QRH for "Standby ASI - Bugs Not Set" as well!

Jeroen Hoppenbrouwers

Don't underestimate the value of a standby bug. You never know when your bug bugs out.


Don't know why Boeing ever fitted speed bugs, or the FMS, or autothrottle, modern rubbish,just give me a good ol' fashioned artificial horizon an ASI (without bugs) and an altimeter, I can do the rest. oh and  copilots ("children")  are surplus to requirement too.
As for the QRH, just unnecessary additional weight


Let's not all lose sight of the big picture.

I don't know peoples' backgrounds here so, while hoping to give a little insight to our non-pilot forum friends and without wishing to teach anyone else to suck eggs:

There are good points on both sides of the argument. We do need to pay attention to details at the appropriate time but I feel that stressing about standby instrument bugs is micromanagement at an unnecessary level. At the same time we also need to take a step back and make sure the very important things are taken care of first - fly the aircraft, navigate and then communicate. This will ensure everything that follows is safe.

You won't fall out of the sky if all your FMCs fail in the cruise or if you don't have an ASI. Why? Because the EPR/N1 and pitch attitude won't change because an FMC or ASI failed. Naturally, you will also have done plenty of home study and rather than worrying about the standby ASI bugs, you will already know your ballpark pitch and power settings at FL350, at FL100 or at circuit height. That will keep you flying!

Once you have worked out what's going on and what you're left with..... you can ask your PM to kindly get the QRH and find the pitch and power tables in the Unreliable Airspeed drill as a back up. These will be referenced against a datum IAS or Mach number. When you brief you can work out the flap config speeds. Feel free to use the bugs in this case if you feel it's appropriate! If it happens on take off you should have the V speeds in your head and can clean up on the placard speeds which are in front of you :)

My point is don't sweat the small stuff. Your priority is to keep the aircraft flying in a sensible direction at a sensible altitude, for long enough to make a 1) safe and 2) (if time allows) economical decision while using your experience and knowledge. Ultimately, command is about managing risk and to do that you need to take in everything. If you are to live, that will not allow you to focus too much or too long on any one single element of the flight. Human Factors.






Good advice but you are somewhat missing the point
you are only considering the notice level of immediate actions
Obviously one has to fly the plane first,
but after that, one also has to project ahead for the consequences of any failure.

Thinking ahead and planning for the event of another failure, be it FMC or engine or outflow valve etc , is also good advice and airmanship, which is why Boeing recommend such actions in the case of failures.

A good commander will also have sufficient experience, system knowledge and capacity to not only think of the 'now' but also the consequences to the rest of the flight

Bug setting here is about thinking ahead, NOT  notice level of a failure

( FMC failure is not the same as Unreliable Airspeed so pitch/power tables not required.
basic Auto Pilot modes are available as is Standby Navigation, just no Auto throttle )


QuoteGood advice but you are somewhat missing the point

Not really, Will's question was about Boeing and airline recommendations about setting the bugs. I think you're promoting the point of view that they should be set at all costs and anything less would count as poor preparation. We're just talking about what's out there :)

Quoteyou are only considering the notice level of immediate actions
QuoteBug setting here is about thinking ahead, NOT notice level of a failure

In the FMC non normal checklist you mentioned above, I think setting these bugs is step 14 or 15 in a customised QRH, it's not an immediate action at all nor is it SOP to depart with them set.

Quotewhich is why Boeing recommend such actions in the case of failures

Boeing and Airbus don't install bugs on every airframe, they are options.

QuoteA good commander will also have sufficient experience, system knowledge and capacity to not only think of the 'now' but also the consequences to the rest of the flight

True, and you should. However, I'd also say there is an infinite number of things that could happen and there is a limit to what you can anticipate and depart on time. You're implying that if you don't set this tiny little bug you're not thinking ahead. In the grand scheme of things, wouldn't you agree bugs on a standby ASI are small fry? Prioritisation. Big picture. But that's just me  :D

As for the Unreliable Airspeed drill, I disagree. The discussion was about setting bugs and so identifying an airspeed to fly, for whatever reason be it loss of FMC, PFDs, marbles etc. Anyway, this was meant more as a general insight into cockpit management for non-pilots. You don't need to apply the drill in order to extract the information it contains. If you're worried that the speed you're flying isn't bugged, fly the pitch and power and you will have the speed. No need for a bug in the first instance. As I said, it's there to be used - if it's installed and the pilot has the imagination, and time, to use it.


I completely agree...

« Fly the pitch and power »

Back to basics

It works whatever of the plane : a Piper Cub or A380

IMHO , standby Instruments are designed to crosscheck the primary instruments.
It is too small to use... from the first officer seat, I can't even see the figures...



No further comments as the thread has become too personal and inappropriate to the good nature of the forum