[time-nuts] Boeing 787 GPS reception trouble

Brian Lloyd brian at lloyd.com
Tue Jun 3 00:59:52 EDT 2014


On Mon, Jun 2, 2014 at 10:36 PM, Jim Lux <jimlux at earthlink.net> wrote:

> On 6/2/14, 7:16 AM, Brian Lloyd wrote:
>
>> On Mon, Jun 2, 2014 at 8:57 AM, Jim Lux <jimlux at earthlink.net> wrote:
>>
>>  O, and since navigation using the ADF and tuning to a AM
>>> broadcast station wasn't unusual.
>>>
>>
>>
>> Well, it is quite unusual for IFR (instrument flight rules) operation. But
>> VFR pilots would sometimes use an AM broadcast station for navigation
>> assistance.
>>
>>
> Back in 1980, the examiner asked me how to do it, but didn't make me do it.
>

He wasn't allowed to. It is not part of the practical test standard for the
private pilot certificate. Still, it is useful.

I have been flying long enough to experience nearly every form of
electronic navigation available in aircraft. I have actually flown an
Adcock "A/N" range. I have landed an aircraft in instrument conditions
using precision approach radar (PAR or GCA). I have used ADF, VOR, DME,
RNAV, LORAN-C, INS, and now GPS. Airplanes haven't changed much but boy the
radios sure have!


>>  I had to learn how to do it when taking flying lessons: it was widely
>>> acknowledged ( in 1980) to be nearly useless,
>>>
>>
>>
>> Not entirely. I still make sure my planes are equipped with ADF (LF/MF
>> direction finding) due to my experience with GPS outages over the
>> Caribbean
>> and Atlantic. I have experienced outages of over an hour where both my
>> panel-mount and hand-held GPS receivers stopped working. ADF was all I
>> had.
>> I suspect that since I was flying a plane popular with drug-smugglers (a
>> Piper Aztec), I was being tracked, followed, and GPS jammed. (I lived in
>> the Virgin Islands, traveling to Florida on a regular basis. I would stop
>> in the Turks and Caicos or Bahamas to refuel.)
>>
>
> I was referring to the "AM station as beacon", and to be fair, they were
> all talking about compared to conventional VOR/DME, and maybe if you had
> one of them new fangled RNAV units that mathematically transformed VOR/DME
> into lat/lon, etc.
>

ADF is less accurate than VOR/DME. It is much less accurate than DME/DME.
It is archaic. But it works. If the beacon is at the airport itself ADF is
amazingly accurate for making an approach. It has a unique characteristic
that it is difficult to jam. (LORAN-C was better and I *REALLY* miss
LORAN-C as a backup to GPS.)

There are large stretches of the Atlantic and Caribbean where the only two
navaids that are available are GPS and LF/MF NDBs. Sure I can use
pilotage/ded-reconing and hop from island to island. But I have now
experienced multiple total GPS outages. It makes me nervous the dependence
we are developing on a system that is surprisingly vulnerable to a
denial-of-service attack.

I do hope that LORAN-C comes back. The original idea of the European
Galileo system to use LORAN-C to distribute DGPS data was brilliant. The
DGPS datalink was itself a source of high-quality time and position
information that is nearly impossible to jam. What a concept!

Has anyone considered how a large-area GPS outage would effect us? I
*really* don't like having all my eggs in one basket.

-- 
Brian Lloyd
Lloyd Aviation
706 Flightline Drive
Spring Branch, TX 78070
brian at lloyd.com
+1.916.877.5067


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