What is "Corrected N1"

[ptwaugh]

Hi,

I would like to understand what corrected N1 was is, and possibly how it is computed.

Thanks.

[zerozero]

Are you sure you got your terms right?

Or maybe provide a little context to your question.

Good luck.

[Old Smokey]

Your question is a little short on detail, but my thoughts run to N1 corrections to be applied to, for example, Takeoff N1 in situations such as (1) Anti-Ice ON, (2) Packs OFF Takeoff, or even perhaps the N1 correction to be applied in a reduced thrust (Flex / Assumed Temperature) Takeoff.

The first 2 examples I've given apply to acquiring the correct N1 from the standard figures after application of a non-standard engine bleed (Standard = Packs ON and Anti-Ice OFF).

The latter case is a deliberate intervention by the pilot to acquire a reduced Takeoff thrust at less than the maximum permitted.

I hope that I interpreted your question correctly.:)

Regards,

Old Smokey

[cavortingcheetah]

:eek:
This is from so long ago and a distant memory and it may be completely useless, wrong even, but, in days of old when one used to fly a King Air 200 and 100 around Africa there were N1 correction graphs in the performance manual?
One extrapolated these figures for NI which were based on altitude and IOAT and put them into tabulated form. Then at cruise the actual NI was read off and noted in the tech log on each leg. This was the NI corrected for altitude and temperature and so long as it was above the figure which we now had in tabular form then this 'corrected' NI was within limitations.
Hope that is of some help and actually would be interested to know from more up to date aviators if the old grey cells have served one correctly with reference especially to that stalwart of turbines the PT6.
Blast Off!!!:D

[enicalyth]

Hi cav chat!
N1 corrected to keep the ratio of N1 to square root of theta a constant where theta is temperature ratio in absolute units. One example. If OAT is -56.5 deg C and N1 is 86.71% what would it have been at 15 deg C on the bench?
Add 273.15 to deg C to obtain deg K.
Theta is 216.65/288.15
Sqrt theta is 0.8671.
If N1/sqrt theta is constant then N1 would have been 100% on the bench.
Absolute bolleaux of course. N1 depends on other things besides. Mind you Rollers used it in the design of Merlin superchargers where they simulated altitude by machining special sets of reduction gears to create the desired ingest temperature. So it must be true-ish. But always remember constants aren't and variables won't.

[Brian Abraham]

On one helo I flew under certain conditions the N1 was biased (the word used and I guess has the same meaning as "corrected"). When OEI the N1 became biased (indication became biased if good engine was above 94% and the bad engine below 66%) with the limits being 101.7% for 2.5 minute power and max continous at 101.2%. The N1 gauge had an ambient temp and pressure altitude input so the electronics in the gauge could perform the necessary magic and the fact that the indication was biased was indicated by the decimal point in the read out flashing. Should the electronics fail a reference in tabular form was on the instrument panel to which you could refer. At sea level and 10C for example you would have to pull 102.7% in unbiased mode for 2.5 minute power. Max continous was .5% less. Depending on pressure alt and temp the bias was never more than 1%. A functional check was made on the first start of the day to check the accuracy of the bias computation in the N1 indicator. Hope I have explained clearly enough.