Positive Rate?
 

How do you determine positive rate of climb? Out the window, VSI, or IVSI?
Is there a "legal" definition or common sense?

Cross check

1. VSI (sorry IVSI, assumuption on my part)
2. Rad Alt
3. Altimeter

:ugh:

............and, I would add, pitch attitude?

If you have an engine failure on a heavily loaded poor performance type the lag in a VSI can be a problem. Once you are off the ground you have a positive rate....waiting for a significant VSI display of this before retracting gear can result in a very long, very slow and very low fly bys.

BOAC, how is pitch attitude an indication of performance?

One would also add:
4. ASI (Airspeed increasing)

This one wouldn't! Improper pitch control on take-off can lead to large speed increase while destroying RoC and with engine failure in most twins, ALT and IAS gains are mutually exclusive. Personally, I wait for rising runway symbol to get to about 1/4 of its way downward (it's 50 ft RA on my EADI) and keep going lower, then I call "gear up".

Objects on the ground get smaller and the altimiter shows a positive rate of climb after the slight lag.

The 737 classic manuals now say "Verify a positive rate of climb on the altimeter".

QAR - you obviusly have yet to see some of the rotation 'techniques' that I have!:)

Don't forget the clicks of all the relays and interlocks as the ground sensors do their thing. The VSI may show a transient on rotation before the main gear get off the ground.

I listen for the clicks, THEN confirm with altimeter and VSI (which is usually the last one).

You have positive rate in the 737/200 when you see in the baroaltimeter increasing altitude.

The only "click" that may be audible in non EFIS type aircraft is the landing gear lever latch solenoid.

If the landing gear lever can't be raised after take off, Boeing procedures state the the gear must remain down. Flaps up on schedule. After flaps are up and lights are out, and if the takeoff configuration warning horn remains silent and if the trust levers are beyond the vertical position... landing gear lever override trigger pull... landing gear lever up and off.

BOAC, Pitch attitude is not an indication of aircraft performance. I welcome you to come flying with me and I will demonstrate the pitch attitudes to which you refer and not only will I be able to do so in level flight, but also with an indicated rate of descent.

I am crediting you with being a Professional Aviator, so it with great discomfort that I ask you to return to Excercise 19 of the PPL syllabus. The attitude/attitude indicator is merely an indication of just that, not aircraft performance.

QAR, I used to teach that, hence my post 'I would add'. Let me put it another way - given that your 3 cues look fine, but the a/c is at that time de-rotating, would you be happy to call 'positive climb'?

I hear at least 3 distinct clicks in the 747 Classic. Besides the landing gear lever, there could be the air spoiler limit lock, T/O autobrake switch, reverse throttle lock...

The following is a quote from the PanAmerican B707 AFM....

Select the landing gear up after confirming a positive climb is indicated on the pressure altimeter.

True then, on this old design, and true today, on new(er) aircraft.
Is the pressure altimeter the most accurate and reliable instrument for indicating a positive climb is established?

Then, as now....absolutely.

I'd tend to suggest that a pressure sensing device, mounted on or near the nose of an aircraft, while that aircraft is perhaps both rotating and/or moving through ground effect may not be the most reliable indicator of absolute altitude. I've certainly seen the raw pressure data do unusual things during the unstick portion of a takeoff. I would suggest that the radalt has at least as good a chance of being an accurate indicator (with its own caveats regarding terrain profiles and the effect of pitch attitude, of course)

That may well be true, Mad (Flt) Sceintist, however I did leave out one word in the quote presented, which might mitigate your concerns...

"Select the landing gear up after confirming a sustained positive climb is indicated on the pressure altimeter"

BOAC,
The aircraft can be, and sometimes MUST be, "de-rotated" (I prefer a "decrease in target pitch attitude"), to maintain a positive rate of climb. For example; if the rotation is to the all engine operative target attitude, and an engine failure occured at the rotation or shortly thereafter, then a positive rate of climb could well result. However as speed started to fall below V2 a decrease in pitch to the engine-out target attitude would be required to maintain airspeed and, ultimately, a postitive rate of climb. In the all engine case, over-rotation may also require a decrease in pitch attitude while still maintaining a positive rate of climb.
Apart from all that, lesson #1 states that POWER + ATTITUDE = PERFORMANCE. QAR ASR would like to demonstrate this to you! In all types rotation is always to the "target attitude" and then performance is checked and attitude adjusted as required by performance. Performance can only be indicated by performance instruments (in this case some combination of IVSI, Altimeter, RA or VSI). Also more than one sustained indication is required, especially in older types where instrument lag and VSI rotation error (rotational forces leading to an indicated rate of descent) may be a factor. Flight manuals, or training manuals, will give this information for the applicable type.
As for "clicks", well it's an interesting theory, but those clicks could be loose objects falling from the galley benches or whatever. Reminds me of a reject at moderate speed when a mobile phone went off during the take off run! The guilty party was in the jump seat and closely related to the skipper!