Re: Bird Strike Detector for Jets??

mrdarrett@xxxxxxxxx wrote:

On Mar 11, 6:49 pm, "Paul Hovnanian P.E." <p...@xxxxxxxxxxxxx> wrote:
mrdarr...@xxxxxxxxx wrote:

[snip]

If you want to design aircraft better, start here:

http://en.wikipedia.org/wiki/Gimli_glider

"The 767 was one of the first airliners to include an Electronic
Flight Instrument System (EFIS), a system that required the
electricity generated by the aircraft's jet engines in order to
operate. With both engines stopped, the system went dead, leaving only
a few basic battery-powered emergency flight instruments. While these
provided basic but sufficient information with which to land the
aircraft, a vertical speed indicator - which would indicate the rate
at which the aircraft was sinking and therefore how far it could glide
unpowered - was not among them."

Michael

I began working on the 767 electrical power systems shortly after this
incident. There were a number of systems that were discovered to have
been left off the standby power system (the barry power).

We also ran into a problem in that the system incorporated a static
inverter with a 1 kVA rated output. The original design had only
utilized about 50% of its capacity. Unfortunately, its rating had been
specified assuming linear loads. While the Boeing specs limited the
current THD any load was allowed to draw, loads of less that 200 VA were
exempt. And most of the loads supplied by the inverter were small and of
the non linear variety (power supplies mostly) with up to 30% current
THD.

After the Gimli incident, the missing bits were moved on to the inverter
bus, whereupon the inverter refused to produce an output voltage within
spec. The loads were taken back off. Since my responsibility only
extended to the power system, when I asked where the loads were put, I
was told to shut up and mind my own business.


Wow, friendly. Were you working for Boeing directly, or for one of
their subs?

Directly. That was when they still did some engineering in-house. But no
more.

Would doubling the VA rating have helped?

The proper solution(s) (which we implemented on the 747-400 and on) were: To
spec a new static inverter capable of supplying nonlinear load currents,
and to remove the exemption on power quality for smaller loads.

And, are the batteries changed out periodically? (They wouldn't
happen to be lead-acid, would they?)

There is an involved maintenance procedure for the batteries. And they are
wet cell NiCad, 24V 40 Ah.

One of my more interesting projects was doing an analysis for a failure mode
where the battery charger gets 'stuck' in constant current mode and
electrolyzes most of its water, producing H2 gas. Its basically a problem
in electrochemistry. Since most chem data is in CGS units, that's what I
used for the analysis (the desired result was a percentage H2 concentration
in air, so it really didn't matter). When I submitted the results, my boss
started throwing a fit about how Boeing simply didn't used metric units. I
didn't want to introduce the possibility of an error due to units
conversion, so if he wanted it re-done in furlongs per fortnight (yes,
that's what I actually said) he could have someone else do it. The document
remained as is.

--
Paul Hovnanian paul@xxxxxxxxxxxxx
----------------------------------------------------------------------
Have gnu, will travel.
.

Relevant Pages

  • Re: Bird Strike Detector for Jets??
    ... electricity generated by the aircraft's jet engines in order to ... inverter with a 1 kVA rated output. ... specified assuming linear loads. ... extended to the power system, when I asked where the loads were put, I ...
    (sci.electronics.design)
  • Re: Bird Strike Detector for Jets??
    ... electricity generated by the aircraft's jet engines in order to ... inverter with a 1 kVA rated output. ... specified assuming linear loads. ... extended to the power system, when I asked where the loads were put, I ...
    (sci.electronics.design)
  • Re: Bird Strike Detector for Jets??
    ... electricity generated by the aircraft's jet engines in order to ... specified assuming linear loads. ... While the Boeing specs limited the ... extended to the power system, when I asked where the loads were put, I ...
    (sci.electronics.design)
  • Re: Bird Strike Detector for Jets??
    ... electricity generated by the aircraft's jet engines in order to ... inverter with a 1 kVA rated output. ... specified assuming linear loads. ... extended to the power system, when I asked where the loads were put, I ...
    (sci.electronics.design)
  • Re: Bird Strike Detector for Jets??
    ... If you want to design aircraft better, ... inverter with a 1 kVA rated output. ... specified assuming linear loads. ... extended to the power system, when I asked where the loads were put, I ...
    (sci.electronics.design)