Technical Update – April 2015

Posted on 8th May 2015 in News

Updates to CAP 437 Standards for Offshore Helicopter Landing Areas – New Requirements to Monitor Lightning

Author: Dr Alec Bennett PhD MInstP FRMetS CMet

We have conducted a technical review of the latest CAP 437 guidance for helipads.  The following sections have recently been updated and now include the need for the monitoring and reporting of the threat (or presence) of thunderstorms and lightning.  To be able to meet these new requirements an in-situ lightning detection system could be required by all accredited helidecks.

We are highlighting these significant changes because we believe that our new BTD-300 thunderstorm (lightning) detection system meets and / or exceeds these new requirements and could be added to all existing helipad operations.

CAP 437:

Chapter 6:

Subsection 4.3.1:

“The latest weather report from each installation should be made available to the helicopter operator one hour before take-off. These reports should contain:”

… present weather (including presence of lightning); …

Similarly, thunderstorm and its attributes are required to be included in present weather (inc. in the vicinity – within 8 km for CAA):

2.4 Present Weather

2.4.1 Only the following weather phenomena are required to be reported:

  • Thunderstorm (No Precipitation)
  • Thunderstorm with Rain
  • Thunderstorm with Rain and Snow
  • Thunderstorm with Snow
  • Thunderstorm with Hail
  • Thunderstorm with Heavy Rain
  • Thunderstorm with Heavy Rain and Snow
  • Thunderstorm with Heavy Snow
  • Thunderstorm with Heavy Hail
  • Thunderstorm in the Vicinity
Subsection 2.3:

“When lightning is observed, it should be included in the [weather] report”.

Section 3:

Pre-flight weather report form has a box specifically for “Lightning present: yes/no”

Incidence of lightning induced accidents

In addition to the changes to CAP 437, there are recent reports of helicopter accident statistics mentioning lightning.  For example in Oil & Gas UK Health and Safety Report 2013 (for period 1992-2012):

“For accidents caused by external factors, 86 per cent of them were because of weather related events, including five lightning strikes and an encounter with a water spout. The final accident accounts for the remaining 14 per cent and was due to a very heavy helideck landing caused by adverse helideck environmental effects (caused by hot turbine exhaust plume).”

“Eighteen reportable non-fatal accidents have also occurred since 1992.  These include major component failures, pilot error, lightning strikes, major airframe damage, and main and tail rotor damage.”

Report can be found at:

The helipad Met Observer training course has the following relevant parts in their latest training syllabus:

  • Identification of convective clouds and the operational significance of TCU/CB clouds
  • Observing and reporting lightning and thunderstorms

The BTD-300 would be an ideal instrument for monitoring / warning of both of these situations.


CAP 437 now highlights the monitoring of thunderstorm and lightning activity.  If that monitoring is to be conducted in-situ on the platform / helideck, then the BTD-300 is an ideal solution.