welliewanger

Hi all,
I'm not a test pilot, but tomorrow I'll be F/O on a C of A test flight of a large bizjet. I'd be interested to hear the opinions of professional testers on a few issues:

1. Stalling. Having instructed on light singles, stalling seems to me to be no big deal. However "older and wiser" pilots have been known to skip this part of the test or not do the full stall test.

2. Single engine. Like with stalling - during light twin training you spend half the time trundling round on one engine. But twin engined jet drivers get all nervous about shutting an engine down in spite of having loads of extra power, reliability and safety systems which aren't included in the light twins.

3. Any tips on how to carry out the flight well.

Many thanks.

Snow Dog

1. Stalling - your aeroplane has a stick pusher. You need to ask yourself why.

2. Single engine - if you wait too long, you may find N1 at zero. You'll need to fly around until the engine cools symmetrically before you can relight it. Make sure you are in an appropriate bit of sky to 'trundle around'.

3. Plan ahead on the ground. Chair fly it and touch drill it. You're an FI - think a lot about link flying.

Let us know how it goes.

sycamore

Wellie, don`t know which country you are in,but a Cof A flight test should only be carried out by an `approved` pilot/crew, ie CAA/FAA/relevant country Authority.He/she/they ,should have all the relevant Flight-test forms/proformae,and you as a crew should/must have had a full briefing to discuss who does what,where/when /how/what you are going to do,and more importantly what you do if if it doesn`t behave.....not just half an hour before you get aboard.
Anyone who does the stalling must have a good appreciation of the handling characteristics of the aircraft ,and recovery from a stall,in all configurations.
Likewise,engine shutdowns/relights,performance climbs on one are required to verify performance,and handling.

Any `older/wiser` person that `skips` some parts of the flight-test ,and possibly signs that it`s OK is being a `fraud`,and they should not be `in the seat`,as it will invalidate the F-T,and in any accident,invalidate the insurance.Obviously ,if weather/serviceability precludes part of the test,then it will still have to be done later,to clear the aircraft.
If you are in the UK,then you should call the CAA F-T Dept,and on the CAA website ,go to the Airworthiness Section,and look under `Flight testing` for fuller/further information. Above all,know the limitations in the ACM/POH,and refresh the `Handling` aspects . Suggest you also read about the `Perpignan A320 accident,and the 737 Airtest.
A full airtest will take probably at least a couple of hours,and for parts of it a large chunk of airspace,under radar control. You should also speak to the controlling Authority(ATC) about suitable areas for use,airspace blocks,non-deviation for certain tests etc..
In retrospect,it should all have been sorted last week,not as a fast-ball on Monday mornings, however, I hope you are successful,but don`t expect it to be a `walk-in-the-park,until the chocks are `in`,and the fans have stopped..

edit; There is an AIC with regard to `stalling and recovery` you should read; the flight test is to determine the `stalling characteristics of the aircraft`, and recovery; it is not to recover with minimum height loss,as you would teach a student...

Mad (Flt) Scientist

I'll just add to the above - plan for whatever you're testing not to work.

You're not testing to determine the generic characteristics of the type - that was done to get the type certificate. You're testing to confirm that the specific aircraft behaves the same as the type design, and has been built properly.

So, for example, your a/c has a stick pusher. What's the plan if it fails to fire? How will you know it should have fired? Is there anything you can check before the point of no return to increase confidence it will fire.

You're not checking boxes - or, if you are, you're setting yourself up for a nasty outcome. You're deliberately violating normal flight limitations to the point where rather than systems like the stick pusher being the final safety element, they are going to be the only safety element. Best to have a plan B.

Genghis the Engineer

Excellent advice above, just a few further thoughts:

- Time spent constructing good clear test cards will not be wasted: a standard PLOG isn't appropriate to the task. If your Captain is an experienced flight tester they should be able to give you examples. Always get enough information down on the cards to report without whatever automated data taking is also there.

- The crew should be current enough on the manoeuvres to be flown on a "known good" airframe before conducting them for test purposes.

- Try and schedule it in a manner that avoids unwanted time pressures; if you need to take an extra half hour briefing or debriefing, it should be available to you. Take a long time over the brief, make sure you are both fully happy with the test cards, talk through each manoeuvre.

- It is dangerously easy on tests like this for both crew to get heads-in worrying about the tests. Make sure that one of you is attending to all the usual airmanship/management/lookout issues at all times. I've been known to use "I have lookout", "You have lookout" in this environment, in a similar manner to "I have control", etc which works well. This is a layer of activity on top of everything else you are already trained to do, and needs to be recognised as such.

- Always have agreed "knock it off" criteria throughout. If you reach them, just RTB, if things are going "funny" debate it on the ground, not in the air.

- Lots of free information at Flight Test Safety Committee that's worth reading through.

G

sycamore

Probably a bit late now, but you should know WHY the a/c is being tested,ie is it just a Cof A renewal,or has it been spread all over the Hangar and now reassembled in an eye-catching manner,ignoring the box of `left-overs...?
If the former,it may be fairly straight forward; if the latter,, beware!!
If there has been any recent maintenance,read up what `snags`/gripes/frequent`things` have been written-up,and rectification has been carried out to clear them.Was a pre-maintenance airtest carried out before maintenance, as many `snags` possibly been `carried` but not written-up..Above all,do not be tempted to sign it off,unless you are absolutely positive about it`s serviceability,as it is your integrity in the end...

welliewanger

Thanks very much for the info guys. The flight has been postponed a few days so I have some extra time to prepare. The aircraft is Hong Kong registered and the authority require it to be tested on initial registration and then once every year. I was F/O on the last flight (with a factory test pilot) and this year am flying with an "ordinary" Captain who has been signed off for the job. Last time it took the best part of three hours.

I've thought through the possible outcomes of shutting an engine down and am comfortable that I know (and can theoretically resolve) most of the potential problems. Stalling is another matter. The potential problems I foresee are:

- Deep stall. Solution, recover promptly. Prevention is better than cure!

- Wing drop. Solution, rudder AS REQUIRED. Normal unusual attitude recovery techniques.

- Spin. Do 30 meter aircraft really spin? I would imagine that it would all happen so slowly that you'd only ever get as far as the incipient stage and just centre the controls to recover.

Of course, all of these could take significant altitude. What have I missed?

sycamore

W-w, it would be of interest for us to know the type,no need for reg, so that maybe someone with test experience could comment..

goldeneaglepilot

Most aircraft will spin, many are not cleared for spinning. Think of the film Top Gun - it was a spin that killed Goose!!!!

What does the test flight schedule require you to do for the approval flight test? - If you need to be asking, then perhaps a pilot trained and signed off to do the test should be P2 - Is the aircraft certified only as two crew operation?

Mad (Flt) Scientist

The correct solution for "deep stall" is indeed not to get there. if you do - and it would take an effort - then you are not getting out without help from above. Its not just "recover promptly" though. Its knock-off criteria. Awareness of when the pusher should fire and readiness to jump in if it doesn't.

Wing drop. if the wing drops in the stall, and you're slats IN, something very nasty may be about to happen. Rudder isn't the cure - get the alpha down, immediately. (That's basically the cure for all stall problems, simplistically). If the wing drops a bit during the slats out stalls, well, a bit of roll activity is possible - the wing has stalled, after all. But anything abrupt is the cue to get out of there.

Also, for the slats out configs, don't dawdle in the shaker to pusher region. You don't want a high entry rate - but the target is 1 kt/sec. Going in slow exposes you to the high AOA environment for longer. Who knows what might happen to ruin your day if you stay in a part of the flight envelope that's usually a no-go zone.

Spin. Haven't seen one do that, but highly swept aircraft can do funny things at high combinations of AOA and sideslip - if you let the yaw build up you're asking for one wing to stall first, and while it might not be classic spin, some degree of autorotation is possible, once one wing lets go.

@ Sycamore. According to WW's profile, it's almost certainly a Global Express. The above comments are predicated on that assumption.

welliewanger

@Mad (flt) scientist and sycamore. You're not only a good test pilot, but also a good detective! It is indeed a Global, for those unfamiliar with the type, it's similar to a G5 (BIG HIGHLY swept wing, engines at the back, T tail)

@Goldeneagle. I have the test schedule here and am studying it. I have done one of these flights before, but unlike last time, this time we will be doing the full schedule (including engine shut down). The parts which worry some people are:

- Engine shutdown FL160 less than 250kts with APU running. Then test systems and climb capability. Then windmill relight.

- Stalling below FL150. "Stop deceleration if stick shaker has not occurred by 3kts below scheduled speed or if pusher has not operated by 2kts below scheduled speed"
What's the big deal about stalling an aircraft like this? People seem to get very shaky about wing drops etc. Maybe I've just got complacent with stalling "benign" aircraft like the C152. My personal favourite in that was to stall with full power and a steep turn! Do big aeroplanes really bite you on the bum that much worse?

Snow Dog

You're asking good questions then throwing in naive comments like "What's the big deal"!

How does aircraft size stop it spinning? A high T tail has its problems, but the effects of highly swept wing are very sensitive to any sideslip (yaw). You'll have seen it in the GLEX on asymmetric thrust. Stall with sideslip and one beautiful wing has less lift; the other beautiful wing is generating loads of it. Could that be another reason you have a stick pusher.

Read Sycamore's post again and look up the accidents and fatalities.

It was pilots with the "What's the big deal" frame of mind that has, rightly, triggered an interest by EASA into the different 'levels' of flight test.

Mad (Flt) Scientist

Not too much below FL150, please.

Those "stop decel" criteria are (some of) your knockoff criteria. Those tolerances are the largest normally expected variation in shaker and pusher speeds. If you've got 4kts below predicted shaker speed and nothing has happened, it means that something 'strange' is going on. Best to give up, go home, and work out what is not right on the ground, rather than persevering and finding out the hard way.

The big deal is that the aircraft NEEDS the shaker and pusher - it does not have a stall that meets the certification requirements without those added systems. If everything goes according to plan its safe enough, but if someone failed to do the mx properly on the SPC, or something has happened to aletr the wing characteristics, like a misrigged slat or some such, you might be pushing the envelope.

The difference with other types such as the "benign" aircraft you mention is that they are designed to be stalled. The Global isn't. Its designed to stop you stalling it. You're going to deliberately ignore all the stuff put there to deter you and do it anyway.

sycamore

W-w, if you need any clarification on any part of the FTS,then I suggest a call/email to the factory T-Ps,soonest. I would also hope that you are discussing it all with your `Captain`.I`ve never been in a G-E so have no idea of whether it`s `all-electronic,FBW,sidesticks` or whatever,so anything I`ve said should be taken in that context.
It may be useful to have a third pilot aboard,as an extra pair of eyes,ears,and as a `conductor/scribe` in that he can take notes,listen to r/t.run thru the next test-point,noting any warnings checking configurations etc,lookout,as it will allow the handling pilot more freedom ,without checklists/f-t schedules /paperwork to be floating around whilst you may be `heads-down`.
A couple of other maybe handy tips; A piece of coloured wool ,about a foot long ,taped in front of the centre windscreen,is a good `heads-up` instrument for yaw...I know 50cent instrumentation on a $40m jet !; if you have traditional wheel control,then set your ailerons at neutral,ie surfaces inline,then mark the wheels and columns in such a way that you have a `visual neutral` position for the ailerons (Tippex can be used ,or even
mascara or lipstick !). I always carry a mini tape-recorder,either taped to the mic. ,or the `phones `inside the helmet/headset,and stick the plug
in the `mic` socket.. I also carry a mini GPS data -logger( $50) from H-K),but I`m sure you`ve got all the fancy CVRs/FDR

Going back to the stalling,and I`m sure M-FS will concur,the starting position will be usually at about 1.3-4 Vs,in trim,idle power or as rqd, followered by a gentle deceleration aiming for ,ideally 1 kt/sec .speed reduction.Now this may take a couple of tries,and will be in a shallow descent,usually,not as student teaching,ie level flight,otherwise you will get an accelerated stall,and pushers/warnings can go off at the wrong speeds/incidence..Count it down clearly..
Personally, for stalling/spinning,I always use two hands on the stick ,as this minimises any lateral/aileron input( good reason for marking the neutral aileron position,as it is critical on swept wing a/c ),and don`t,don`t use aileron or rudder to `pick-up-a wing`,UNTIL you have lowered the nose positively,got rid of any `buffet`,irrespective of your attitude....and your airspeed is increasing.Power should be increased as required,but beware that as you pass thru` your original `trimmed speed` the a/c will want to pitch-up,again ,irrespective of your attitude. Remember ,coarse use of ailerons/rudder anywhere near the stall may well aggravate the situation.
Syc...going for a cuppa..

Neptunus Rex

willie

If you are in Hong Kong, there used to be several ex RAF and RAAF test pilots in Cathay who had done their courses at ETPS or Pax River. The ones I knew would be only too happy to help you. Try a trawl in Fragrant Harbour, or call the HKAOA.

Lou Scannon

Find a graduate of ETPS and put him in the left seat. I am not one. But I have sat watching company "aces" doing air tests and taking forever to complete profiles compared with how someone with real test training and experience would do it.

...and if things go wrong the trained pilot will have the better chance.

Pilot DAR

One important thing I have not noticed within all the excellent advice here, is a discussion about who will fly, and what the non-flying pilot will, and more importantly not do, if something unexpected happens. This has been the greatest source of challenge when I have done flight tests with a pilot, with whom I have not before flown. This pilot probably will not understand why I'm going to do, how far I'm going to do it, what I will do if something unexpected happens, and what I expect of them. Entry into a stall with a wing dropping is NOT the place to suddenly find out the other pilot's level of comfort with stalls, and you flying them! I made this error once, and never again. Now my co pilot gets a very through briefing (one hour plus), which centers on all the things I will do if something goes wrong.

I explain that I will not stop flying the aircraft at any point, unless he or she says "I have control" - then they have it, all of it! and that may not be what they are expecting. I then ask about their recent flight test and aerobatic experience. With my improved briefings, flights have been going much better, and generally I find that there is no question about who will fly at any time during the flight.

If you are properly flight testing an aircraft, you are doing a whole bunch of things that "line" pilots are trained to specifically avoid and prevent. This can create real cockpit conflict at the very worst times.

If the other pilot is doing all of the flying, expect to be told what your role will be, and stick to it. Trying to "help" fly, would be a very unwelcomed thing to do, unless asked.

Brief (or be briefed) well, fly safe, and take it slowly, according to the plan....