Are we departing illegally in C172R if NOT using short-field? technique

[2211race]

In the Cessna 172R model flight manual, there is only one take off configuration.
Shortfield take off.
There are no figures at all for any other type of take off.
How do we know the take-off distances for any other take-off, say, a zero flap take-off?

What if we did a zero-flap departure and crashed the plane on take off?
Would the insurance company & CASA ping us for not using the techniques described in the POH ?
Would that be an illegal departure?
Would the courts agree that we "made up our own way of departing" as it's not an approved method?

[MakeItHappenCaptain]

Cessna manuals only specify short field technique for the performance. You will find further description in the normal procedures checklist and in the associated take-off amplified procedures (Section 4). I will check the 172R specifically but all others from memory specify 0-10 degrees for take-off. The amplified procedures specify a 10% reduction in distance to 50' with flap and the correct speeds.

The short field distance is best case scenario. If you have more distance available, you will be able to get out legally.
Don't forget your 15% allowance over the factory figures as per the CAOs.

[ravan]

Not illegal per se but....... if you crash, then "tell the court in your own words why you elected to not use the technique specified in the POH".

Which is not to say that the short field technique is the only way, only that if you use any other technique you are wholly responsible for the safety of the outcome of your technique.

[bentleg]

What if we did a zero-flap departure and crashed the plane on take off?


You are operating as per the manual when departing with 0 deg flap.

172R Skyhawk Information Manual - Section 4 -Normal Procedures - Wing Flap Settings Page 4-25 says -


Normal take offs are accomplished with wing flaps 0 to 10 deg. Using 10 deg wing flaps reduces the ground roll and total distance.........etc

[2211race]

Yes, section 4-25 does discuss 0-10º Flap setting, still no distances although there is a mention that 10º flap "reduces the ground roll and total distance over an obstacle by approximately 10 percent"
So, zero flap departures are OK provided you add 11% to the figs on page 5-14
plus the CAO20.7.4 (section 6) CASA factor of 1.15 (aircraft <2000Kg)
Although, that 15% is not very clear that it IS a requirement if using the flight manual figs...
if you read CAO20.7.4 section 6
6.1 states 'subject to paragraph 6.3' then mentions the 1.15 factor requirement
6.3 states to refer to to either requirements in 6.1 and 6.2
OR
'the requirements relating to the take-off distance in either of those manuals (approved foreign flight manual or manufacturer's data sheet)

6.1 is subject to 6.3 which refers to requirements in 6.1 and 6.2 OR use the flight manual...
The "OR" to me means there is no requirement to refer to 6.1 and 6.2 (factoring 15%) if using an approved foreign flight manual.
you can use the tables in the manual without having to factor 15%

Am I reading this correctly???

[mcgrath50]

Shouldn't there be a take off distance chart somewhere, and that's how you figure it out based on conditions and weights?

[mstram]

"The short field distance is best case scenario"

.. or "worst case", depending on your point of view :)

[bentleg]

Shouldn't there be a take off distance chart somewhere, and that's how you figure it out based on conditions and weights?

Read the original post. There is a take off distance chart for 10 deg flap, but no chart for 0 deg flap.

means there is no requirement to refer to 6.1 and 6.2 (factoring 15%) if using an approved foreign flight manual.
you can use the tables in the manual without having to factor 15%


Figures in the flight manual are "best case", new aeroplane and skilled test pilot. Adding 15% is a sensible thing to do, you would be crazy not to.

[swh]

One would hope you consult the appropriate flight manual, not information manual. The flight manual is approved for the specific aircraft.

[john_tullamarine]

(a) Shouldn't there be a take off distance chart somewhere

There used to be but the baby was thrown out with the bathwater a long time ago when the old DCA manuals (and the initial GAMA manuals with the Australian extra data) went the way of the dodo.

(b) be aware that the US GAMA manuals are part FAA-approved and mostly, not.

(c) for a first approximation with different speeds/configurations, distances can be factored by the ratio of the speeds squared

(d) main problem is to have a good story for the enquiry if you come unstuck. ie, if the strip is anything near what the the POH suggests you need, then use the POH data configuration.

[bushy]

If you cannot achieve the figures in the approved flight manual you really should go back to flying school for more training.
You don't need to be a "test pilot' with a new aircraft and a lot of luck.
The approved figures are factual and if you use proper techniques you can achieve them.
The manufacturer would be sued out of business if they published incorrect figures in a flight manual.

[MakeItHappenCaptain]

One would hope you consult the appropriate flight manual, not information manual. The flight manual is approved for the specific aircraft.

The cessna info manual these days IS the approved flight manual.

Thank Christ we can get away from the old typed CASA manuals! (Although the TO/Land charts were OK)

Back to original question, I would suggest if you have more than (the short field figure) / .9 available, ie the nil flap distance before the 10% reduction, then you could use a nil flap take-off.