Turned out to be relay with high resistance on the contacts inside the Stab/speedbrake control box.

Only the dark lines are a possibility.

 

 

 

 

 

 

 

 

 

R console dimmer on G-IV

Dimmer at MED floorboard 1.

Inverter at copilot rh rudder pedal

 

 

EGPWS_OVERLAY2

New to me (2022)

Chemical:

Sub-heading:  “what is this black crud all over the terminals?”

 

it is possible that the production of this black residue combines with water to reduce the resistance on fuel probes and wires, resulting in increased ability to make house payments.

 

 

I have witnessed this so aggressive, it would deposit a “pile” of black dust on the lower tank skin, below each terminal.

 

 

 

These are the barrels on a KDAL based G-IV, 1 year after extensive cleaning.

 

One local GV accumulates a brown varnish oh the outside of several probes.  It is very smooth, consistent thickness, almost clear ,  light tan .  It coats the outer tube so heavily, you can scrape it off like a varnish.

 

Here is a research paper…. way over my head

ar03-61 (1)

This sentence seems significant:
“the rate of corrosion was approximately linear with concentration of elemental sulfur (up to a level of 1000 ppm),”

This from the summary:

“A significant conclusion of the work described herein is that the active and deleterious inorganic component of the deposits is silver oxide; the roles of copper and sulfur both appear to be secondary and to suppress conductivity. The electrical properties of deposits formed naturally in
fuel tanks, or grown under representative lab oratory conditions, can cause misreading in presently employed electrical FQIS system.”

Looking for an old Air Force article that talks about the change from DIEGME to IEGME for biocide.  That caused paint stripping of sealant and primer.

This aint it, but its close

Sub Heading: Why is there gooey buggars inside my fuel lines.

I think the “Apple Jelly” phenomenon is related to double load of Prist, and higher than normal amounts of water in jet fuel. So called because of contamination in Alberta Products Pipeline (APPL). Apple Butter almost took down one of my clients Falcon 10 corporate jets.

 

 

Biological:

Sub-heading: “Why does my fuel tank stink like a sewer?”

I think i have observed this several  times. 1 falcon 900ex 2 months following a possible over application of BioBor.Result was 7 condemned probes in the wings.  I could not save any of the 7 probes by slosh/clean/dry/repeat method.  Very unusual.

Microbiological:

Characterization of microbial contamination in United States Air Force aviation fuel tanks

• Original Paper
• Published: 22 November 2005

• Volume 33, pages 29–36, (2006)
• Cite this article

Abstract

Bacteria and fungi, isolated from United States Air Force (USAF) aviation fuel samples, were identified by gas chromatograph fatty acid methyl ester (GC-FAME) profiling and 16S or 18S rRNA gene sequencing. Thirty-six samples from 11 geographically separated USAF bases were collected. At each base, an above-ground storage tank, a refueling truck, and an aircraft wing tank were sampled at the lowest sample point, or sump, to investigate microbial diversity and dispersion within the fuel distribution chain. Twelve genera, including four Bacillus species and two Staphylococcus species, were isolated and identified. Bacillus licheniformis, the most prevalent organism isolated, was found at seven of the 11 bases. Of the organisms identified, Bacillus sp., Micrococcus luteus, Sphinogmonas sp., Staphylococcus sp., and the fungus Aureobasidium pullulans have previously been isolated from aviation fuel samples. The bacteria Pantoea ananatis, Arthrobacter sp., Alcaligenes sp., Kocuria rhizophilia, Leucobacter komagatae, Dietza sp., and the fungus Discophaerina fagi have not been previously reported in USAF aviation fuel. Only at two bases were the same organisms isolated from all three sample points in the fuel supply distribution chain. Isolation of previously undocumented organisms suggests either, changes in aviation fuel microbial community in response to changes in aviation fuel composition, additives and biocide use, or simply, improvements in isolation and identification techniques.

 

Here is a USAirforce study about biologicals

jimb0029

MECHANICAL: