VRC
Hi to all VRS fans out there. So what's a nice guy like me doing here on a warm Easter Sunday morning ... I logged on to the thread at 08.00 hrs and two hours later seem to have covered more than 280 or so posts.
That's something I love about pprune ... being able to read the studies and experiences of the likes of Shawn, Nick, and the other highly experienced and knowledgable guys so there's no question of any egg sucking lessons coming from me. But as a 14,000 hr rotary guy - can I put in my two pennorth and relate some adjacent VRS experiences.
First I'm a trifle concerned to know I have been teaching what apparently is an incorrect VRS recovery technique in advocating zero use of collective lever ... my reasoning being that whilst it may assist recovery due to the reduction in downflow, the associated loss of height is unacceptable in a real situation.
So at grass roots level in training for the VRS exercise, I demonstrate the well established, One-Two-Three technique.
Having completed the pre-exercise checks, 'Number One' is to select a suitable LS picture albeit from altitude with power set to provide a suitable ROD (circa 60 knots.) Once settled in a steady descent ...the establishment of the 'Number One' condition for VR is emphasised.
VR requirement 'Number Two' is introduced with aft cyclic to progressively reduce speed at some 5 knots per second to below translational lift speed.
I like to point out the change in airframe attitude and increase in ROD as translational lift is lost. As has been said here, it is important that aircraft attitude remains steady if we are to find that elusive VR tube of air! With the VSI indication showing an increase, I invite my pilot to increase ROD with a further lowering of lever.
Now we need to wait for say 5 to 10 seconds as the airframe settles in a steady but increased ROD. The establishment of the 'Number Two' condition is emphasised.
With a solid vocal warning, condition 'Number Three' is introduced with a firm,(possible panic mode) raising of lever. In the case of the Enstrom/SH300/MD500 series, the usual indications are: airframe buffet, random yaw and roll, disc flapping and RRPM variation invariably accompanied by an increase ROD. The right yaw can be quite severe but recovers .. see later.
To achieve the condition, which for the first 20 or so seconds is incipient, it is important the pilot uses minimum control inputs, especially with cyclic. Recovery is the usual forward cyclic to obtain a positive ASI reading before applying power.
The highly experienced FE who does my client's skills tests prefers the combined cyclic AND collective lever recovery, so this method is also shown, while I emphasise the extra loss of height that may not be adviseable in a real situation.
Now here is where I need help.
I explain to my pilots that the random yaw, (always right in the above mentioned types) is due to the loss of T/R effectiveness in the disturbed air, but the self-recovery is due to the T/R blades finding smoother air at the edges of the disc. On one occasion I experienced a rapid 90 degree disc roll to the right which I decided was due to the M/R blade tips doing a ditto. Not a good explanation perhaps so the whiz kids invited to explain please.
Following the rapid roll experience, I do recall my gentlemanly Irish 500 pilot saying at the time ... 'Dennis - please can we not practice that particular exercise again.'
Just a closing note and as I have written elsewhere - being intrigued by the off-quoted airflow reversal as the upgoing air punches through the centre of the disc - I decided to investigate by super-glueing a couple of dozen wool tufts to the fixed mast on a SH 300 and then running through the VR exercise. The 300 has excellent overhead vision so I was delighted to find my tufts flapping nicely in the turbulent airflow with their tails now obediently pointing skywards! A Eureka moment for me. I'd found the airflow reversal!
As has been said, let's keep this subject going for ever for all to read.
Take care all ppruners. Dennis K.