[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

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