Takeoff with a light coating of frost, up to 3 mm (1/8 inch) in thickness on lower wing surfaces due to cold fuel is permissible. But, all leading edge devices, all control surfaces, tab surfaces,upper wing surfaces can't have snowor ice.

How about the upper surface of the wing?Jack C

In summaryFAA regulatory requirement 14 CFR 121.629b states that no person can takeoff with frost ice or snow adhering to critical surfaces, but, takeoffs with frost under the wing in the area of the fuel tanks may be authorized by the administrator.So my final answer is:Frost on top of the wings means no takeoff.Frost under the wings due to cold fuel up to 3mm is allowed for takeoff. (if the administrator says "go for it")

In summaryFAA regulatory requirement 14 CFR 121.629b states that no person can takeoff with frost ice or snow adhering to critical surfaces, but, takeoffs with frost under the wing in the area of the fuel tanks may be authorized by the administrator.So my final answer is:Frost on top of the wings means no takeoff.Frost under the wings due to cold fuel up to 3mm is allowed for takeoff. (if the administrator says "go for it")

I was looking at old info for the top wing.-it can't be more than 1.5mm thick-extent of the frost must be similar on both wings-the frost is on or between the black lines for permissible cold-soaked fuel frost, with no ice on the leading edge or control surfaces-the ambient temp is above freezing-there is no precipitation or visible moisture.

Hey Dan. Your answer is a very reasonable one but on the NG you can take off with frost on the upper surface but under certain conditions. Does anyone know what they are?Jack CWoops I see you made the post just above this one as I was typing. So I see you found the answer! good job.

I amended my post above your last reply Jack.

I was going to ask a question relating to fuel temp probes but then thought "is that really useful info?". I said No. So here goes a different question#9 If a GPS goes u/s how is the pilot able to tell? How about if BOTH GPSs go u/s?

Hey Dan. Your answer is a very reasonable one but on the NG you can take off with frost on the upper surface but under certain conditions. Does anyone know what they are?Jack CWoops I see you made the post just above this one as I was typing. So I see you found the answer! good job.

Yeah, I was looking at the Boeing powerpoint about it and didn't go far enough into the slides the first time.:(

GPS Light on the aft overhead.If illuminated (amber):• indicates failure of both GPS sensor units• indicates failure of a single GPS sensor unit when either system annunciator panel is pushed.

GPS Light on the aft overhead.If illuminated (amber):• indicates failure of both GPS sensor units• indicates failure of a single GPS sensor unit when either system annunciator panel is pushed.

You got it. BUT there is another thing that will tell you the GPS unit is u/s too. Hint: its on the forward panel of each pilot

The clocks go into manual mode?

It's on whenever 115V AC is applied to the aircraft.

No.

GPS-L INVALIDGPS-R INVALID will display on the CDUs

No.

depends on the voice recorder switch position:Auto- powers the CVR from first engine start until 5 mins after last engine shutdownON- powers the CVR until first engine start then trips the switch to auto.

The first indication of rise in oil pressure from either engine start trips the CVR on.

From where does the No. 1 DC buss receive its power?What is the buss load?