Re: Anti-collison lights

From:         ehahn@fairlite.mitre.org (Ed Hahn)
Organization: The MITRE Corporation, McLean, Va.
Date:         16 Feb 94 13:13:51 PST
References:   1 2
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In article <airliners.1994.927@orchard.Chicago.COM> kchan@jplsp2.jpl.nasa.gov (Khee Chan) writes:


   >Now, why would they do this?  What are the pros and cons of each?

   For the bits that are required to generate the flashes, the following applies:
   Rotating beacon == mechanical == moving parts == more maintenance
   Strobe == electronic == no moving parts == less maintenance

   The difference between the type of anti-collision lights on the above mentioned
   727's is probably more likely to be correlated to the vintage of the aircraft.
   Maybe customer preference has something to do with it - perhaps someone from
   Boeing can answer this.
   -----
   Khee Chan
   kchan@jplsp.jpl.nasa.gov, kchan@esoc.bitnet, jplsp::kchan             
    <<I speak for nobody and nobody speaks for me, sometimes not even myself!>>
---
I'll take a shot if you don't mind.  I agree with you regarding the
maintenance aspects of the two systems, first off.

>From an operator's perspective, whether an airline would standardize
at all, or even which to standardize would depend on the following:

1) Operator experience in component consumption (how many burned out
lights/motors, etc.) on a per year basis,

2) Spares commonality with other fleets.

3) Spares which would become obsoleted.

4) Engineering manpower to write a modification order and CERTIFY it.
(Could be non-trivial, depending on which region of the FAA the
operator reports to).

As with most operator decisions, the economics usually decides:

For example, Airline X has 20 B727s, mostly delivered before strobes
became an option.  Airline X also has 10 B737-200s, which happen to
use the same mechanical system components (I don't know for sure, I'm just
creating a hypothetical case).  Airline X operates mostly in the
southern part of the US, without much time spent in salt environments.
They also tend to fly a daylight charter schedule.  Airline X's
consumption of parts is rather insignificant compared with the cost of
retrofit.

Example 2:  Airline Y has 95 B727s, about 30 of which were delivered
before strobes were an option.  Airline Y, which flys mostly cargo,
operates a heavy night schedule between Chicago and Florida/Caribbean.
After getting rid of all of its B707s, the airline only has newer
aircraft like the EFIS MD83 (aside from the B727s).  The yearly
maintenance costs for the older system has been increasing over the
last few years.  Because the newer aircraft are all strobe equipped,
it may make sense to retrofit these aircraft, especially since the
management has decided to hush-kit these aircraft to meet Stage III
noise regulations.

Now I will wait for the usual bandits to pick apart the details, but
you get the idea.  ;-)

Hope this helps,

ed
(ex. American Airlines/Trans World Airlines Avionics Engineering)

////////   Ed Hahn | ehahn@mitre.org | (703) 883-5988   \\\\\\\\
The above comment reflects the opinions of the author, and does not
constitute endorsement or implied warranty by the MITRE Corporation.
Really, I wouldn't kid you about a thing like this.