Is the helicopter “Dead Man’s Curve” really a death sentence? Jonny Greenall challenges a common misconception about the Height/Velocity (H/V) Diagram, explaining what it means, how it affects helicopter operations and why understanding the risks matters more than simply avoiding the shaded areas.

The Dead Man’s Curve – Myth, Reality and Helicopter Training (According to Jonny)

Question: What is the "Dead Man’s Curve" and how does it limit our training profiles?

Quick Answer: it isn’t called that, and it doesn’t….

Long answer: Read below

Based on the Robinson Helicopter Types – other types may differ…

The actual reference is the “Height / Velocity Diagram” and is only called the “Dead Man’s Curve….”  by people who do not understand the basics of helicopter performance.  

The graph is Height against Velocity, giving some shaded areas where operations should be avoided for certain speeds and heights.  It is found in Section 5 – Performance of the Pilots Operating Handbook

In the words of the FAA:

“Height-velocity tests are conducted to determine the boundaries of the height versus airspeed envelope from which a safe landing can be accomplished following an engine failure.”

Basically – operating within the shaded areas does NOT mean instant death in the event of an engine failure – it means that a safe engine out landing may not be achievable.

Isn’t that the same thing?  Not quite

How the H/V Diagram is developed

Firstly, let’s look at the certification requirements, and how the testing was conducted.  Each helicopter type is required to undergo their own certification – so do not assume that “one size fits all”

Smooth Hard Surface – so testing was conducted onto a smooth hard surface for landing.

Wind Calm – so in a no / light wind situation, so no assistance from any wind

Weight – the testing must take place a Maximum Weight

Damage – the helicopter cannot sustain any damage in anyway, nor can the occupants be put in any hazardous situation.

Testing – is done in 3 areas – level flight, take-off and high speed

1 Level flight – it is the upper region of the shaded area.  So, level flight, but there is an additional allowance of a 1 second delay between engine failure and the pilot actually moving any control

2 Take-off – the lower portion of the diagram, that runs low level and roughly parallel during the transition phase of flight and then turns up toward the level flight section – this is called the knee.  There is no delay in pilot action in the event of an engine failure

3 High Speed – this is the low-level, high-speed section on the bottom right-hand side of the diagram.

The company test pilots need to perform these tests, and then they are checked by the FAA to prove compliance.  Do they break helicopters during these tests – absolutely!  Then it is back to the drawing board to increase the shaded area and retest.

Can I, as a pilot, make the H/V Diagram “better”?

Absolutely…  you can give yourself an even bigger margin of safety, and you should – this is the basis of a good pilot demonstrating good airmanship.

Surface - Try to take off over a hard smooth area….

Wind – take off into wind, any wind on the nose will improve your safe landing chances.  Concurrently, if you really really really have to take off down wind be aware as you have just increased your risk of exposure

Weight – if you are below MTOM, then you will have a bigger margin of safety

Damage – the skids have some impact resistance built into them, also required at certification.  Beyond this they are designed to bend and spread the load to allow for the safety of the helicopter occupants.  Remember, helicopters can be repaired, people not so well.  If you have to sacrifice the helicopter to save you and your occupants – do so.

1 Take-off – there is no delay in pilot action – NEVER take you hand off the collective until at a safe altitude and speed as in the event of an engine failure your reaction needs to be immediate.

3 High Speed – well, it’s fairly obvious…  if you feel the need to be “hooning around” at high-speed low level, and the engine stops you are in a whole world of hurt.  Have a very good reason why you need to expose yourself and your passengers to this risk.

Time – Limit the amount of time you are ever in the shaded area of the H/V Diagram and be acutely aware that you are operating in that environment.

Checks – Make sure you have the performance to operate in the shaded area of the  H/V Diagram and do all the safety checks you can to ensure that you are reducing your risks whilst operating.

Is it the same for take-off and landing?

A big misconception - NO – the H/V Diagram was developed for take-off and level flight.  In these regions you will have the collective at a higher pitch angle than descent, you may also have a rate of climb, that you would need to convert into a rate of descent in the event of an engine failure.

Does it limit our training profiles

Absolutely not – in fact we must teach and train the students how and when they should operate in the shaded area of the H/V Diagram, the risks and how to avoid them.

Risk Mitigation

It is well known in the industry that some of the biggest threats to helicopter operations, especially off airport, is wires and tall obstacles (trees for example) sticking out in our way.  The larger risk of hitting a wire or obstacle against the much smaller risk of a mechanical engine failure means that entering the shaded area momentarily could be the best captaincy decision.

If you are a helicopter pilot and didn’t know about the above give us a call (or ask your flight school for your money back!)…..

At Balearic Helicopters, we believe good training is about understanding why, not simply memorising what. Whether you're a student, a qualified pilot or an instructor looking to sharpen your skills, get in touch with Jonny and the team to discuss your helicopter training.