What is that green rectangle next to altitude readout on Boeing aircraft?

Question

Does anyone know what this green rectangle represents? It's from a Boeing 777 PFD. I can't find answers anywhere.

score 14 · Accepted Answer · answered Feb 18 '22 at 15:40

14

It indicates that the altitude is below 10,000 ft.

My Boeing 777 FCOM shows the same rectangle in the PFD description, but does not mention any details about it.

However, the Boeing 747 FCOM includes more details:

6 Ten Thousand Digit Display

Cross hatch displays when altitude is below 10,000 feet.

^{(Boeing 747-400 FCOM 10.10.28 - Flight Instruments, Displays - Controls and Indicators)}

answered Feb 18 '22 at 15:40

Bianfable

@J... I think it's more that 10,000ft is a magic number for "are we higher or lower than those mountaintops" reasons – Jack Deeth Feb 19 '22 at 17:15
5

@JackDeeth I very, very much doubt that... there are hundreds of mountains above 10,000' all over the world (and similarly, many huge regions where far lower altitudes are safe). The idea of 10,000' being any kind of safe-altitude rule of thumb is ridiculous. – TypeIA Feb 19 '22 at 18:15
@J... and there also being space on the display with the 1st digit being a 0 / not present! – Tim Feb 19 '22 at 22:30
1

@Tim I guess that is the primary function - to avoid ambiguity. A black space might allow 3200 to be confused with 32000, and 03200 is just hard to read. – J... Feb 20 '22 at 04:13

score 3 · Answer 2 · answered Feb 18 '22 at 15:16

3

This is a crosshatch marking to show the altitude is below 10,000 feet. See What is the meaning of the crosshatch marking on altimeters?

answered Feb 18 '22 at 15:16

Tevildo

1

Any idea why it's green rather than white? – Jack Deeth Feb 18 '22 at 21:52
4

@JackDeeth My guess is because a digit in that position (above 10,000') would be white, so the green crosshatch reduces the chance of it being mistaken for a digit. – TypeIA Feb 19 '22 at 10:27

2 Answers2