Teaching VRS

[eurocopter beans]

Hi All,

Quick question, is it standard practice to demonstrate Vortex Ring / Settling with power recognition and recovery during helicopter flying courses. I was never actually shown it, just briefed on how to avoid, recognize and recover. Is practicing entry into and exit from VRS beneficial for flight training and if so what is the best way to demonstrate it in a safe fashion (downwind, heavy, etc?)

I would put this in the flight instructors forum but rotorheads never let's me down!

Any guidance much appreciated, as ever.

Eurocopter Beans

[thecontroller]

http://www.pprune.org/rotorheads/332636-do-uk-military-teach-vortex-ring.html

[Brilliant Stuff]

Both my Instructor and later the Robinson Factory showed me VRS in the R22.

If you are not shown how you going to know what the symptoms are like?

[Whirlygig]

Incipient vortex ring state was demonstrated to me during my PPL course. From what I remember, we climbed to 4,000 ft and my instructor actually had a bit of difficulty trying to get into it.

Cheers

Whirls

[Torquetalk]

It's a mandatory item in the JAR-FCL2 licensing syllabus.

It's hard to get demonstrate into wind in the R22 and requires a very high nose up attitude and backward flight. Weight should only affect the ROD at which it commences: bit heavier requires a slightly higher ROD to accelerate.

Lot's of height! 2k+ Downwind, decelerate towards an out-of-ground-effect hover. Keep the nose straight and attitude flat; allow the aircraft to accelerate the ROD slowly until it begins to race away: recover with disk to horizon and slight reductin of pitch. DON'T pull pitch until positive airspeed indicated.

[the coyote]

I used to teach it in a past life, and think it is very important. We were in R22 mainly and also H300. We used to get plenty of height, 3000' feet or more, and pull it up in the hover. For some reason hovering downwind seemed to help (probably because into wind you still might have had some forward speed). Then, slowly and progressively start lowering the collective to descend whilst 'fishing' around for your downwash as you descend with cyclic. When you got it in the sweet spot it would fall out of the sky in the blink of an eye. After doing it countless times, I could tell by the feel when we were close to it and in the danger area, and think this is valuable knowledge to have. It would enable me to recognise and react far quicker than if I had never experienced it.

For those of you who haven't been there, why don't you post what you have been taught? I'd be interested to hear what they say if they only do it in the classroom.

You can't learn it all from a book.

[chester2005]

for my FAA CPL checkride i had to demonstrate it in an R22 and recover from confirmed symptoms into stable forward flight before height loss exceeded 500ft

Chester:ok:

[Mungo5]

Demonstrating it is a standard part of the FAA PPL(h) checkride, you're taught to recognize it and how to get out of it from an early stage in the US.

Some examiners ask for a verbal explanation, rather than a demonstration, as they're not so keen to get into it in the first place.

[delta3]

It was never fully shown to me. During my PPL and in the Robinson Safety course only the on set (vibrations), recovery was explained, not shown.

I got since then several full blown VRS's, mostly while doing high altitude hover pedal turns. As been discussed before in other threads this is due to of a tail-rotor wake interaction that increases the risk (R44-B206), see other suggestions of flying backwards.

Happy that VRS was explained to me, the explained recovery worked nicely...

Need to show? Personally I don't think so, one can just do a high altitude hover (2k+) and kind of show what to do without actually provoking a full blown VRS.

m2c

d3

[Gordy]

This is not a big deal....For 135 training and checkrides I teach it to all my pilots and have them demonstrate it to me. The FAA requires 1500 feet, but in reality you can recover from the initial indications with less than 100 foot altitude loss. Working fires, the times I get into it is coming in hot to a dip site...so I, and the guys I work with need to understand the symptoms and INITIAL indications.....we would probably not recover from full blown VRS at 100ft.

Here is how I demonstrate it---may not be perfect, but it works for me:

I have the pilot fly the aircraft in straight and level flight and then execute a slight nose up attitude and reduce power to less than hover power and HOLD it. Do not do anything else---the aircraft will decelerate, (it may take a while), and as it comes below ETL it will start to descend....again just HOLD the attitude....this allows you to differentiate between the loss of ETL and incipient VRS. Once you feel the nose shudder, you can execute the recovery with less than 100 foot drop from that point.

There is NO need to scare the student/pilot....the purpose is for them to recognize the indications etc.....

[Hedge36]

I can't imagine NOT teaching it to a student... jeez, that's as basic (and about as exciting) as fixed-wing stall training.

[eurocopter beans]

From reading this thread and the previous one concerning VRS training in the military it would seem that the civilians teach incipient recovery but doing the same has gone out of fashion in the military, I would be interested to know why this is the case?

[captchopper]

I was given an engine failure when i was nose down to get out of 'settling with power' in my Commercial check ride... that was something. and yes settling with power should be in training curriculum.

[the coyote]

Gordy, I doubt you are in any VRS at all with what you mention. I suspect the shudder you mention is probably more to do with turbulent air/tip vortices impacting the rotor system perhaps?

I am no techo head, but my understanding is you need a ROD of around 50% or more of the downwash velocity to begin the enter VRS territory. The downwash velocity varies significantly with factors such as rotor design, RPM, density altitude and disc loading at the time. It can be calculated quite accurately.

Here is a quote from Nick Lappos when I asked him the question a while ago:

"To calculate the downwash speed (which is the reference for VRS for a particular helo) just take the disk loading in pounds per square foot and multiply by 210, then take the square root. That will give you the feet per second for the 1.0 speed value.

To be conservative, if you take a descent at 50 to 75% of that descent rate, you can avoid VRS.

Here is an example: For an R-22, disk area 498 sq ft, Gross Weight 1370 lbs, disk loading is 2.75 lbs/sq ft. 2.75 x 210= 577. The square root of 577 is 24 ft/sec, which is the average downwash of an R-22 (24 ft/sec is about 14 knots, or about 1440 ft/min).

This means that the R-22 can't get VRS above about 11 knots forward speed (75% of the downwash velocity), but also that it can't get VRS in a descent less than 700 ft/min (50% of the downwash velocity)."


My experience of VRS is a lot of vibration, very sloppy and compromised cyclic response from the rotor system and an enormous and increasing rate of descent, way beyond that of autorotation. "Lose your guts" stuff.

In my opinion, recovery from "full blown VRS" as you mention will take far more than 100 feet, and may not be possible at all, as the rotor may enter a complete stall if the ROD goes off the scale.

Just a quick example: If your ROD in VRS is say 2400 fpm (auto is around 1800 or so) that is 40 feet per second. So in your recovery it takes you 2 seconds to decide to lower the nose and it takes 5 seconds for the cyclic input to take effect and the airspeed to build beyond ETL, and 3 seconds to try and do something about your huge ROD. There goes 400 feet (or more) in 10 seconds.

I think what you are talking about is more like getting to the open door of the aircraft and deciding to close it before you jump. Once you have jumped, it takes a while for the parachute to open and stop your fall.

Just my opinion!

[chopjock]

Coyote
Just a quick example: If your ROD in VRS is say 2400 fpm (auto is around 1800 or so) that is 40 feet per second. So in your recovery it takes you 2 seconds to decide to lower the nose and it takes 5 seconds for the cyclic input to take effect and the airspeed to build beyond ETL, and 3 seconds to try and do something about your huge ROD. There goes 400 feet (or more) in 10 seconds.

In your example, if it takes 5 seconds for the cyclic to respond, how long would it take just to dump the collective? There is more than one way to escape the VRS.:)

[Thomas coupling]

Gordy - absolute rubbish! You can't demonstrate Incipient VRS without allowing it to show the pilot all the feedback effects [Which I hope we all are aware of].
This will cost atleast 500-1000' height loss! Slowing down inaccurately in preparation for the demo could cost you 100', never mind recovering before this amount of height loss :=
Your poor customers are going away thinking a slight judder and they are in IVRS!!!

Coyote: As an ex mil instructor and currently sim instructor on heavies, I agree with your observations.
What people dont hoist in is that during fully developed VRS the a/c is: OUT OF CONTROL. The pilot cannot take charge of the a/c. It will either crash or fly itself out of the state. The problem with the latter is that it could take thousands and thousnads of feet for it to allow you to regain control.

make NO mistake here. Fully developed VRS is UNCONTROLLABLE!

What happens in real life with these 'instructors' is that they actually demonstrate IVRS and not VRS.

People who search for the real McCoy especially at entry gates of 4000' and below are living on borrowed time IMO.:ugh:

[delta3]

Thomas,

I do agree with your comments, but think that the safety margins depends on type of heli and CoG configuration.

I remember that there was a case of a Puma losing many thousands of feet before recovery (even more than 4K if I remember well), so full blown VRS here, no thanks...

Personally I think that the R44's relatively large horizontal stabilizer at the rear of the fuselage combined with small body inertia helps to create a nose down attitude (even without cyclic input). A B-206 does not do it that easy in my experience.

All comes down to making a balanced risk assessment in the teaching curriculum, see for example the fact that EC fenestron failures need not be practiced any more, because of unfavorable risk comparison.

d3

[Ascend Charlie]

TC says: "Fully developed VRS is UNCONTROLLABLE!"

Ummm... try rolling off the throttle. You are only in a vortex because the rotor system is developing thrust, trying to push air from above into airflow coming up from below.
Go into auto, you fall through all the vortex and emerge into clean air, roll on throttle, with forward airspeed, and hopefully fly away.

[chopjock]

A CUmmm... try rolling off the throttle. You are only in a vortex because the rotor system is developing thrust, trying to push air from above into airflow coming up from below.
Go into auto, you fall through all the vortex and emerge into clean air, roll on throttle, with forward airspeed, and hopefully fly away. Surely you mean lower collective and maintain throttle RPM? Rolling off throttle would loose RRPM if in VRS???

[the coyote]

Chopjock, 5 seconds for the cyclic to respond AND gain some airspeed. Of course I am aware that entering auto is a recovery technique. However, it still takes time and height to gain some forward speed in auto and to then bring the power back in and arrest the significant ROD. You can't just enter auto and raise the lever again with zero airspeed can you? Entering auto does tend to improve the cyclic response though, I have found.

The point I was trying to make was I think it is crazy to think that 100 feet is enough to allow for a recovery from any form of VRS.

[whirleybloke]

During my training on R22s at Cambridge, VR and recovery was demonstrated to me as preparation for my first solo with me following through. Later on in my training I was taught to recognise the incipient staqe and then recover - all very straightforward even though it always seemed a pig to get it there.

My skill test interesting. When I showed I could recover from the incipient stage I was told that was all fine, but let's see what happens if we let it develop a bit further. Yiks! Experiencing the rapid height loss and random control effects and then recovery was invaluable. I guess having an instructor/examiner who is good and you trust is the key.

Gotta be better than just telling someone what it's like.

[RVDT]

The truth is these things are everywhere, you just cant see them -


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[Gordy]

Thomas coupling


Your poor customers are going away thinking a slight judder and they are in IVRS!!!

Firstly I don't have customers anymore--tis a while since I taught students or customers.

Gordy - absolute rubbish! You can't demonstrate Incipient VRS without allowing it to show the pilot all the feedback effects [Which I hope we all are aware of].


Yes I can, go back and read my post---I said recover from "initial indications"...I agree you will lose some altitude in the deceleration. And no the first shudder is not VRS but shortly after when one feels the sudden drop... In my line of current work, I do not have the luxury of altitude...therefore, as I stated, I want to make sure the pilots I work with recognize those first indications, hence we demonstrate it the way we do.

This will cost atleast 500-1000' height loss! Slowing down inaccurately in preparation for the demo could cost you 100', never mind recovering before this amount of height loss

My whole point is that there is no need to get full blown VRS unless you are a test pilot. Why not teach people to recognize the onset and adjust the cyclic accordingly. Hopefully people will never get full blown VRS---they should have corrected long before.

Go out and try this.... Set up, just as I explained before, and then upon the shudder and "tail drop", ease the cyclic forward, pause, ease it back again---repeat a few times and you can get in and out of early VRS quite easily and painlessly. Remember--I am only teaching people to recognize the first symptoms so they can take action. I have no desire to lose 1'000 of altitude demonstrating VRS---leave that to Shawn and Nick.

[Torquetalk]

Ummm... try rolling off the throttle. You are only in a vortex because the rotor system is developing thrust, trying to push air from above into airflow coming up from below.


Er, you mean lower collective, right? Roll off throttle and it's tatty bye, especially in such an unstable state. The engine has nothing to do with VRS or any stage of it: The flow you are inducing with pitch is opposing an inflow from below caused by an increasing rate of descent (which you also said). In auto there is little or no induced flow, so it can be a way out of the condition together with airspeed. Airspeed, however, is the only necessary condition to get out. And as coyote says, getting out of [even!] IVRS takes time and therefore height and as most IVRS situations are likely to develop late in a mismanaged approach to landing you are unlikely to have the height to get out. If you want to race your aircraft at the ground in those last few hundred feet, good luck!

[Nubian]

Thomas Coupling,

What is the purpose of learning about VRS?

What people dont hoist in is that during fully developed VRS the a/c is: OUT OF CONTROL. The pilot cannot take charge of the a/cWell, I have been instructing in a few diffrent types over the years, (civilian) so only those small things which makes the AS-350 the heavy among them, normally at 3000ft AGL.
I have executed the demo more or like the way Gordy was explaining. At first into the wind to show the student how the aircraft will act in a gentle way, then later with tailwind, which is a diffrent cup of tea.
The latter part, I have developed ROD that is increasing quickly past 6-700ft, as well as reduced attitude and yaw-controll (not as you say out of controll, but reduced controll, so reactions to inputs are delayed)
Now, from both demonstrated cases I have recovered with increased speed by forward cyclic to fly away, and I have done the autorotation recovery. All with great success. In tailwind condition, I've usually lost from 4-700 ft. during recovery.
After demonstrations the students have done the same, and the purpose of the exercise was for the student to recognize the onset/initial indications to avoid entering VRS, but also to know how to recover from it.

What happens in real life with these 'instructors' is that they actually demonstrate IVRS and not VRS.
So, does that mean; I have NEVER had VRS in the first place, or should I be lucky to be alive?
How far do you need to hold VRS to qualify for being "in it"??

Now, of course you can make it more extreme by pulling collective after entering VRS, but what will the point of that be? Forcing the student to change underwear after landing or give up flying, period?

I think this part of instruction is more important than shooting autos all day long to "nail" the numbers of some runway in case of engine failure. How many hours are used for that out of a PPL ticket compared to VRS-training?? Not many are unfortunate enough to have an engine-failure, but everyone who gets into a helicopter without proper knowledge about VRS can have it no matter what!


ps: I have never had VRS before or after my instruction-period unintentionally, so maybe my training was usefull after all?! I think that's the main point with training, to recognize the situation before it gets beyond your controll..

[delta3]

Quite interesting so far ...

Perhaps at a risk of deviating a bit from the original question:

"What about showing an engine failure shortly after take off say at 200 feet"

Any opinions on the use / need of showing that ?

d3

[chopper.al]

Delta 3, I have done a few autos at 200 ft after take off (with instructor!)and think this is a very important auto to become familiar with. MCP, low speed and low alt doesn't give much time to react if the engine stops.

On the subject of VRS, I certainly did a few fully developed ones and during my test had to get myself into and out of VRS to the examiners satisfaction. I thought it was normal to do these as part of the syllabus.

[WikiRFM]

This is a great topic. In my primary training, we were required to demonstrate VRS and recovery prior to soloing, and also on our check ride. However, at the RHC course, I realized how inadequate this training was, and figure that during training there was probably a bit of confusion about the vibrations around ETL and incipient VRS. At RHC, the recovery that I'd been doing was completely inadequate.

In the spirit of trying to improve training, I've been publishing lesson plans in a form that allows experienced instructors to provide input for new instructors and students. Check the VRS lesson plan (http://wikirfm.cyclicandcollective.net/wikirfm-pplh/settling-with-power/) out here, and please add your experience.

[Thomas coupling]

Some of you aren't listening are you?
A fully developed VRS stipulates that cyclic/collective*/yaw inputs are redundant. Do you know what that means guys?
It means that you - the pilot, inputs at the cockpit end but nothing is registering at the aerodynamic end.
Once more for the hard of hearing:
The aircraft no longer responds to your demands.
How, therefore, can you recognise you are in fully developed VRS and then at the flick of a switch (cyclic well fwd) withdraw from VRS? :ugh::ugh::ugh:
You can't, because it won't! It will either run out of altitude, or fly itself out of VRS (if it remains upright).

Make NO mistake here. There are only two remaining types of pilot who "demonstrate fully developed VRS".
(a) The majority of them are actually only demonstrating IVRS and genuinely believe it is the real McCoy.
(b) The remainder - actually do demonstrate fully developed VRS and are lucky to still be alive.

IF you had mil training in the 50's and 60's, you may have been lucky (especially in the RAF) or should I have said unlucky, to have been shown fully developed VRS in the Sycamore/Whirlwind. These instructors commenced the manouevre at between 10,000 and 12,000 and often pulled out around 3-4000 feet:sad:

{* The collective is the only way out of VRS - by entering auto the VRS is removed eventually from the rotor plane. The problem with this is that the a/c still has to be upright! And you will have to accept an even higher RoD as auto takes effect. This is the only way out of VRS}.

No-one should ever be in a helicopter attempting this demonstration below (IMHO) 5000' and upwards.
It is my experience that very very few civilian pilots fully understand VRS or have even experienced IVRS.

Please try and get your heads around this for your own sake and those around you who are passengers at the time.:=

[delta3]

Question to the test pilots (Shawn, Nick), in order to help to objectify the discussion:

1. is recovery from a full blown VRS, part of the certification program?

2. is there a formal definition of full blown VRS as opposed to IVRS as part of certification envelop definition ?

thx

d3

[thecontroller]

Teaching certain recoveries
Quite interesting so far ...

Perhaps at a risk of deviating a bit from the original question:

"What about showing an engine failure shortly after take off say at 200 feet"

Any opinions on the use / need of showing that ?

d3

http://www.pprune.org/rotorheads/322974-engine-failure-take-off-do-you-teach.html

[[email protected]]

TC - I'm with you on this one, the data that Nick Lappos posted on previous threads about VRS showed that on something like an R22 you would need to have 800 - 1000 fpm RoD just to get into the boundary of VRS let alone into fully developed VRS.

If you can recover in 400 -700' you are only showing the incipient stage and recovering from it - I have done it in an R22 and 206 for 1179 checks and it is not VRS, it is just letting the aircraft shake a little bit and then recovering into forward flight.

That is not to say that the demonstration is pointless - it is exactly what you want the student to learn, immediate recovery from the incipient stages having recognised the warning signs - just don't call it full VRS 'cos it ain't.

In theory a powerful enough helo can recover from full VRS using power but R22s and the like certainly won't have that capability. Try setting up your VRS demo and then pulling to max power at the onset of vibration - chances are you will stop the RoD immediately but because you only use a small application of lever in the standard demo and have dropped off ETL you have insufficient power applied for an OGE hover and so your RoD increases.

[Nubian]

Thomas Coupling,

What's your point?

WHY, should I want to experience fully developed VRS in the first place, when I'm fully aware of the danger and how to avoid it in the first place???? (the whole purpose of this type of this training is to AVOID it full stop!!!)

With this logic I am wondering:
In all my training giving/receiving doing Auto's, I've done about 90% to a power-recovery, and the last 10% full down, engine at idle. Does this mean in your opinion, that all those auto's has been waste of time, as I have never shut down the engine??

And what do you mean by:

No-one should ever be in a helicopter attempting this demonstration below (IMHO) 5000' and upwards.As in demonstrate the manouvre and recovery as per flight-training requirement? or as you refer "the real McCoy"??? (which I'm in no way interessted in trying out)

Please try and get your heads around this for your own sake and those around you who are passengers at the time.:= I have, and it's time for you to reflect on the need for anyone besides a few (very few) of trying the "real McCoy" :ugh:

[delta3]

Trying to summarize

Full VRS (see posts of Nick, Shawn)

- start with a vertical descent until you reach 75% vi (= 1040 ft/min for an averagely loaded R44)
- until fully developed VRS at 100% vi (= 1390 ft/min)

If lots of power available escaping is possible with power (example = tail rotor VRS's in sideways flying that can be controlled with lots of power)
But even Nick suggests putting nose down and flying out of it (see VRS thread post 232)
Some suggest to go to full autorot if altitude permits as alternative to shed of Vortex (..)

Quite some dangers here (see TC), not to be shown, should be test pilot territory (question: is this part of flight testing envelop similar to plank deep stall testing ? remains unanswered)


IVRS

- vertical ROD between 50% and 75% vi, so 700 - 1040 ft/min.
- or as Shawn, the Coyote and myself say, increase chance of IVRS by provoking tail rotor wake interference via slow backward flight at lesser ROD

Most people suggest to put nose down via cyclic only , some suggest also to lower collective (if lots of altitude is available) to get nose down faster, nobody suggests to use power

"I"VRS should be demonstrated using ample altitude safety margin, up to the instructor how big or small the "I" should be.

Risk factors
- the specifics of the helo aerodynamic configuration (horizontal stabilizer), making it more or less prone to take on a nose down attitude
- vi = weight requiring proportionate descent rates and altitude safety margins

m2c

d3

[topendtorque]

I'd be interested to find out just what flight phenomina is experienced in the famous 8,000 feet descents, but for my money it is not a sustained system of rotor tip vortices. I mean, fair suck of the sav guys, how on earth could those vortices withstand the force of the uprushing relative airflow from directly beneath?

Perhaps it may have been stalled rotor airfoils, something which occupies my imagination a bit, whilst I am demonstrating the maneuvre.

In all the thousands of times that i have done it, in both '47's and R22's, the aircraft will accelerate very quickly and fall vertically but never more than 200 feet at the outside. The altimeter is the only guide, it will all of a sudden show the height lost in one gulp just after the rotors hit clean air and the aircraft slows the descent appreciably.

Usually one can control the exit as one must as if one stuffs up and inadvertantly encouters VRS, it willusually only drop about 80 feet, so remember, if you enter at fifty feet or less it will only ever be the last 30 feet that will hurt.

i disagree that one cannot control the A/C attitude in the vortex state, as the rotor blade is still flying and generating lift in the cocoon of vortices. duh - that is how the vortices are being generated. so use that control to tilt the rotor disc and then it will simply "slice out' of the cocoon of vortex ring, which was attached to the disc.

(and yes also lower the collective A of A if possible, which should also stop the generation of vortex, but I would never roll off throttle with the collective still up, sacre bleu, there would be two of the perfect conditions for rotor blade stall)

similarly when I tried to hold the aircraft upright, the it always fell to the heavy side, with the same slice out effect effect, that is with only the pilot on board of course, remembering that the 'cocoon' that you are in has separated from the surrounding air mass.

demonstrating VRSlearning IVRS and recovery is an absolute must. IVRS is best explained and demonstrated as the commencement of the falling sensation in the pit of the stomach. at that point do something real quick.

as discussed before, jumping it out of the VRS state very early and quickly with collective can be done, but don't go into a state of overpitch by doing so.

the very first time I got caught I did just that. I had descended quickly into a fairly large hole in 60 feet high timber to turn some belligerant cattle, hard and fast like. The ground had been burnt recently and rained upon with a heavy storm straight afterwards, no dust or loose material to show me that the headwind I had on entry was now a tailwind with a just developing willy willy on the starboard side.

i dropped about ten feet and jerked it to stop it at about 2 feet. I had over pitched, I landed carefully and breathed a couple of times before proceeding.

I have no intention of replicating the maneuvre in heavy aircraft, neither do i think it needs to be.

But, if you guys want to argue about a sustained VRS for about 8000 feet, put a bloody smoke generator on your aircraft and film the effect, before going on, please.

[RVDT]

Knock yourselves out -

Free-Vortex Wake Calculations of Helicopter Rotors and
Tilt-Rotors Operating-In and Transitioning Through the Vortex Ring State (http://terpconnect.umd.edu/~leishman/Aero/vring.html#Cases)

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[eurocopter beans]

Thanks for all the inputs, its interesting how VRS / SWP always seems to incite such 'debate'. The aircraft we will be utilising is the EC135. I think it might be beneficial to demonstrate the incipient stage of VRS (as opposed to loss of ETL). If incipient stage VRS is as easy to recover from as indicated on this thread and on some previous ones I can see no 'danger' in starting IVRS at , say, 6000ft and recovering when the student has clearly recognised how it feels to be in the incipient phase of VRS.

When i was taught to fly planks we regularly practiced spins instead of just being told the theory of them and their recovery. When spin training was complete the emphasis was put on incipient stage spin recovery... recognising the initial phase and recovering before a full spin develops, surely the same can be said of VRS. I agree that the risk / reward of entering full and deep VRS procludes entering it, besides you don't want to scare the student unnecassarily (or the instructor!!)

[Torquetalk]

eurocopter beans

You will have to go below "ETL" as otherwise you won't be demonstrating or experiencing anything. Just keep one eye on the VSI and be ready to recover promptly as it accelerates away. Recover right way.

TT