Overpitching isn't Vortex Ring. It isn't Settling with Power. So what exactly is it — and why can it be so dangerous? Discover what happens when you ask your helicopter for more power than it can give you, and how quickly things can go wrong. Understand the warning signs, recognise the risks, and learn why prevention is always better than recovery.

Overpitching in a Helicopter: The Misunderstood Danger

So… what is overpitching?  Is it settling with power, vortex ring or all the same just different names, or something different….  There seems to be some confusion in the helicopter industry on what is what….

Overpitching is a far more common accident than is assumed, and often mistaken for vortex ring.

We need a brief understanding of settling with power and vortex ring before moving onto overpitching.

Settling with Power (NOT Vortex Ring).

This is a “power” problem – the clue is in the name.

You have a “power required to maintain straight and level” – for flight and hover.  If the power available (IE – your engine) is less than the power required, it is impossible to maintain level flight. 

This means that you will descend with power (or settle with power) ….

Example:

Hover out of Ground Effect requires 26” MAP due to density etc.  However, you cannot attain more than 25.5” with the collective.

You are 0.5” short of being able to maintain a Hover out of Ground Effect. 

You start descending, gently, maybe 100fpm rate of descent, and you will just keep doing that…

It is possible to allow the helicopter to increase its rate of descent and enter vortex ring.

Vortex Ring (NOT Settling with Power).

This is an “aerodynamic” problem.

With power applied, high rate of descent and low airspeed, several aerodynamic factors come into play.

Firstly – you will need a very large amount of “power” which means that the main rotor blades will have a considerable pitch angle to maintain lift.  So, the inner section of the main rotor blade will already be stalled due to the angle of attack and low rotational speed.  This reduces the total area available to produce lift.

The blade tips increase their recirculation, due to the high pitch angle.  This also reduces the total area available to produce lift.

Then, if you add in a descent rate things start to get “interesting” ….

The recirculation increases as you descend into you own downwash, so lift area on the outer portion of the blade decreases, however, the airflow now moving upwards at the blade root also increases the stalled area of the blade.  The 2 combine to rapidly reduce lift across the blade (or disc) and suddenly you are, in the words of the press, “plunging or plummeting” to the ground below.

Overpitching (NOT Vortex Ring nor Settling with Power).

Guess what… this is a “pitch” problem.

Your engine is capable of producing a finite amount of power.  Known as your “power available”

The engine has a job to do, basically push your blades around.

The rotor blade produces lift and drag.

The engine's job is to provide the torque required to turn the rotor system, overcoming drag and maintain rotor RPM.

If you raise the collective and increase pitch the drag increases.  This means the engine needs to work harder to overcome the drag and keep pushing the blade to produce RPM.

But remember – your engine is a finite resource.  You cannot just keep raising the collective.

Eventually you will reach 100% of the engine power, so all the engine is being used to overcome drag and maintain RPM.

If you raise the collective beyond this point, there is only one thing that can happen.

The engine will continue to overcome the drag, but as there is no more engine left, it will come at a cost – Rotor RPM.  So, the Rotor RPM will begin to decay.

The blade is “overpitched”.

The more you raise the collective the more overpitched the blade will become and the lower the Rotor RPM will drop.

The answer to fix this?  Stop the blade being overpitched!  - Lower the collective reducing pitch, and if available open the throttle at the same time!

However, it is slightly more complex than that…

The risk of overpitching is when you are at high power settings (and therefore high blade pitch).  This means that the high-risk areas can be approach, departure, HOGE, or specialised areas where you are flying slow (EG – photography).

Approach

As you start to lose translational lift you will need a significant amount of power to reduce the rate of descent and meet the power required to hover.  If you need more power than the engine can produce you will overpitch, RRPM will decay and your Rate of Descent will start to increase

Option 1 – your natural instinct will be to try to stop the aircraft descending, so you will raise the collective, but this will just make things worse, very quickly!  You will eventually rotor stall and hard land.

Option 2 – you recognise the helicopter is starting to overpitch.  Your reaction is to lower the collective whilst rolling on throttle.  However, this means that your rate of descent is also going to increase, so you will hard land, but at least with RRPM and some degree of control

Prevention – on final approach check a few things… are you into wind, are you heavy, is the approach too steep or too fast, do you have the power to actually land what how you want to?  If it doesn’t feel right, then Go Around early and plan B.

Departure

As you accelerate from the hover to forward flight, the aircraft will momentarily sink, this needs to be arrested by raising the collective, it is possible to overpitch in this scenario.

Option 1 – as you accelerate, you raise the collective and the RRPM decays, aircraft sinks.  To prevent the aircraft sinking you raise the collective, this reduces RRPM further and increases the rate of descent, you hard land

Option 2 – as you accelerate, you raise the collective and the RRPM decays, aircraft sinks.  You lower the collective and roll on the throttle, however, this also causes the helicopter to sink, you perform a run on landing, hopefully the ground beneath you is suitable!!

Option 3 – completely counter intuitive, and not recommended, however, you could attempt to accelerate the helicopter more, this will means passing through translational lift and suddenly additional power becomes available!  Hopefully you won’t hit the ground attempting this manoeuvre otherwise bad things happen….

Prevention – you did you hover check didn’t you?  Power available and power required – what was the difference?  A hover check is not simply something you do because the checklist says so. It tells you what the helicopter can actually do today, in today's conditions, at today's weight.

HOGE

When trying to hover out of ground effect you will need a lot of power, and if there is insufficient power you might overpitch the helicopter trying to hover.  Hopefully in this case you will have the height to recover.

Also note, if you allow the rate of descent to build you may inadvertently enter vortex ring as well!

Prevention – do your performance calculations before flight.  If maximum available power is reached and the helicopter will not hover OGE, pulling more collective will not create more power.

Photography

Scenario – you are orbiting, low and slow over the subject, as you turn downwind you are being pushed by the wind, so you slow down further.  You are looking at the subject and not watching your aircraft.  The classic trap is that your attention is outside the helicopter because you are concentrating on the subject. Meanwhile, airspeed is decaying, the wind is changing and the helicopter is demanding more power.…. You raise the collective to prevent the sink, and now you start to overpitch.

Prevention – be very aware of your speed and wind direction when operating low and slow!

Correlator

I need to mention the correlator at this point.  That wonderful mechanical device that helps you, the pilot, keep the RRPM in the green.  However, in this case the correlator in not your friend!

As you lower the collective the correlator will automatically reduce engine power, as that is exactly what it is designed to do – this means that, when RRPM is decaying, lowering the collective, whilst removing the blade pitch also has the unwanted side effect of reducing the RRPM – just when you need it most!  This is why the pilot action is to simultaneously open the throttle and lower the collective!

Governor

The governor is not the recovery system for a developing overpitch/low-RRPM situation.

The governor is designed to maintain rotor RPM by adjusting engine power by electrically controlling the throttle linkage, but in a rapidly developing overpitch condition it cannot respond quickly enough to prevent rotor RPM decay once the engine has reached its available power limit.

Factors Effecting Over Pitching

Hot – increased temperature

High – increased altitude

Humid – increased humidity

They are all related to density altitude and will reduce helicopter performance and reduce engine power availability — a double whammy!

Prevention – Do your performance calculations before flight!

Heavy

The heavier you are, the more lift you need to overcome your weight, so the more blade pitch and hence more engine power needed, thus reducing your margins of power available and power required.

Prevention – Do you weight and balance calculations before flight!  Remember that the helicopter doesn't know whether the extra weight is a passenger, fuel, baggage or equipment.

Engine

Hopefully the engine is in tip top condition and producing the power it should!  However, it could have a potential issue, magneto failure, partial power loss.

Prevention – the hover power check, or if in flight a suspected partial power loss you should have been trained to deal with the issue - you have haven’t you?

Airframe

Dirty blades lead to a significant increase in drag, meaning you’ll need more power to overcome the drag.  Same for ice and frost!

Prevention – keep your helicopter squeaky clean!  Improves performance massively!

Wind

Helicopters like being into wind, wind is free lift, so use it!  Crosswind and downwind will mean more power is used to overcome the out of wind situation.

Prevention – where possible, and if safe to do so – fly into wind!

Final Note

Overpitching isn't a mysterious helicopter phenomenon. It's simply what happens when we demand more power from the helicopter than the engine can provide while maintaining rotor RPM.

Recognise it early. Understand your helicopter. Know its performance. And, most importantly, don't put yourself in a position where you need to recover from it.

Overpitching is one way of getting yourself into low rotor RPM, but low rotor RPM can have other causes — engine problems, governor problems, throttle/control issues, excessive aerodynamic demand, incorrect operation, etc.

The pilot's immediate concern is the same: maintain rotor RPM and keep the helicopter flying.

Find out why afterwards.

First, fly the helicopter