Flyingplanner

Our Bulldog failed its airtest following C of A because it was 140' below expected 900' climb rate. The aircraft manual uses a table with the variables of aircraft weight, altitude and temperature. I have used the data and I get a much lower expected climb rate-nearer 800' expected.
Can anyone help in advising me of the parameters I should be using?

The data for the test was Airfied Altitude 321'AMSL. Temperature 21 C(ISA +6) Pressure climb 1200'-4700 (average alt 2950). Airfield Pressure 1030mb. As far as I am aware the pressure element does not affect the temp I should be using in the manual but what average height should I be using. Thanks

camlobe

I have to ask, why are you posting your question on here? If your aircraft has failed its rate-of-climb, I woud guess that an experienced engineer is the one who has advised you of this. If this is the case, then he will have used the Flight Manual for your specific aircraft, incuding any performance write-downs supplied by the CAA in the form of Change Sheets and Supplements.
If you have flown the airtest yourself, and can't get the figures right, have a chat with your engineer. After all, he is the one who has to sign it as acceptabe to submit to the CAA.

P.S. when was the last time the aircraft was weighed?

camobe

Flyingplanner

I have the aircraft performance data and as I said in my original post I get a substantially different expected rate of climb from the data sheet inputting the information from the flight as I understand it, bringing the aircraft well within the expected climb performance. Unless I have got this totally wrong. The engineer has rechecked the aircraft and says there is nothing wrong with the engine performance/prop etc. The aircraft has recently been reweighed. As yet we haven't managed to speak to the pilot undertaking the test. So my question stands using the performance data sheet my suspicion is that there may have been a miscalculation in ISA temp of +5C explaining a difference in 100' climb performance. The aircraft is awaiting a repeat of the climb performance element of the airtest.

barit1

If the organization will approve it, I would request a side-by-side ROC check with another Bulldog in formation. There can be other advantages to this too - visible drag producer(s) etc.

NutLoose

Personally if the day was warm or a bit bumpy I would redo the climb on a cooler day........ Have known several to fail on warm days only to pass on cooler ones........ also it may be the prop if nothing is obvious drag wise, do you have access to another one... they can untwist, sending it to the likes of CFS they will be able to retwist it for you.......

john_tullamarine

....if the day was warm or a bit bumpy...

.. surely these tests are being done in a structured manner ... calibration-checked gauges, basic power available checks, if necessary rigging checks .... ideally around dawn, nil inversions, nil turbulence, nil wind, reduced to standard conditions, etc., etc..... ?

.. otherwise, why bother wasting one's time to get Mickey Mouse data ... ?

NutLoose

Quote:

....if the day was warm or a bit bumpy...

Yes the tests are carried out to a laid down structure, but even with the best will in the world a light aircraft will not always reach the figures on a hot day or bumpy day.......... I know it may sound strange, but it does happen and often an airtest has to be carried out on pilot availabilty when the weather and conditions are not conducive to optimum climb rates.... that is why I said if it was warm or bumpy try again.....
I did one aircraft on the UK reg that has NO climb figures published by the manufactures believe it or not........ In the end the caa read the previous figures out to me over the phone and we went by them as a guideline.

As for the mickey mouse data......... well bar those on annex 2 that is now irrelevent as there is no longer a requirement to carry out Airtests on EASA aircraft every 3 years or indeed at all, unless you have specific doubts or concerns, as is the norm with the FAA in the USA....... that is in my opinion a BAD move....... I would rather know that the twin etc etc we have just air tested will maintain height on one, even if it won't climb but just maintain it... rather than find out when it's needed that the engine you are now running on will just take you to the crash site....

I would check the prop though, but the engineer dealing with it will know its age, history etc, more than me, LAMS in its latest format has that the Prop must be overhauled IAW the manufactures recommendations.... something that not everyone may be aware of as in the past a fixed pitch item was generally on condition, whilst a wobbly item was on calender/ hours.

john_tullamarine

... airtest has to be carried out on pilot availabilty when the weather and conditions are not conducive to optimum climb rates ...

.. but that's the whole point .. you're wasting your time and shouldn't even bother turning and burning ... go to the pub and come back when you have nice stable air sitting overhead. Going flying is a waste of time and the data prove not much at all other than we went for a fly ...

Mad (Flt) Scientist

But, John .... the Schedule!!!!

john_tullamarine

Indeed !!

.... my schedule is

(a) 1000 ... first beer
(b) 1100 ... second beer ......

Lutefisk989

did you consider wind...sawtooth in reciprocal headings?

NutLoose

Quote:

... airtest has to be carried out on pilot availabilty when the weather and conditions are not conducive to optimum climb rates ...

Again sometimes this simply cannot be practical, if say the Aircraft is out of C of A....... Now in the old days a year or so back, I could simply self issue a fitness to fly and the aircraft could then do an airtest, ferry to a place of maintenance etc........

But post EASA that is no longer the case...something that is a backwards step as you now have to send off an appplication, the CAA has to look at it and once upon a time forward it to EASA to get signed then it had to come all the way back to me before it could fly........ This is fine in theory, but if it requires several tests over a period of time say to rectify such as the above then it could draw out to months simply to get the paperwork in place. This means you try to get the airtest in before the certificate expires hoping that the aircraft passes even if the day is warmer than you would like.

Fine but at the end of the day what does that achieve? All I can see is it achieves extra bureaucracy and red tape whilst generating several layers of extra pen pushers....They must have modelled it after the NHS....

I could understand it from the point of view we do not want aircraft flying around without a valid C of A all over Europe ..... but again with the ARC the C of A will be continous, even EASA wanting to take the control back from the Engineer certifying it fails, as the only person physically inspecting the aircraft and deeming it to be acceptable is the said Engineer, he then recommends it.

All EASA does is a paper exercise that the responsible Engineer did in the past... A simple system of issuing a fitness to fly by the Engineer would have made more sense, as was carried out in the past......... perhaps requiring a phone call to your local office informing them of the reason for carrying it out so that a reference number to add to the form could be issued by the CAA etc.... this way the ball ache could be taken back out of the system.... EASA would be aware of when tests were taking place and have tracibility of them and the Engineer would simply be signing it on their behalf as was the sae in the past.......

Mad (Flt) Scientist

@JT

I think Boeing's new 787 schedule will require a more hardened drinker than that! Perhaps there's a job for me in Washington state after all!

john_tullamarine

... even if the day is warmer ...

I wouldn't worry too much about the OAT as that can be addressed by reduction methods. The problem is to do the tests with stable air, at dawn, and give yourself the best chance of getting reasonable numbers ..

Perhaps there's a job for me ..

.. and, if you find a job that requires less than 70-80 hours a week .. do let me know some contacts .. I could do with a semi-retirement job ..

NutLoose

... even if the day is warmer ...


was just shorthand for all the rest


.. and, if you find a job that requires less than 70-80 hours a week .. do let me know some contacts .. I could do with a semi-retirement job ..


bloody part timers

rodthesod

Don't forget standing waves. If you're downwind of a range of hills and you fly in the nice clear air between cloud bars, you're almost certainly in a descending airmass. Fly under the leading edge of the lenticulars and you could easily double your ROC.