The death of a woman after an incident involving a helicopter landing at a Devon hospital was caused by "systemic safety issues", a watchdog has found.
The Air Accidents Investigation Branch (AAIB) investigated the "fatal accident" in March 2022 at Derriford Hospital, Plymouth.
Jean Langan died from her injuries after being "blown over" by "downwash" - a rapid change in air.
The AAIB said hospital landing sites needed addressing at "national level".
Mrs Langan suffered fatal head injuries at Derriford Hospital in Plymouth in March 2022 during the incident.
The 87-year-old had attended a hospital appointment and was walking through a car park close to the helipad when the incident happened.
A second woman in her 80s, who was also blown over, was treated for a broken pelvis.
Crispin Orr, chief inspector of air accidents, said: "Our in-depth investigation revealed systemic safety issues around the design and operation of hospital helicopter landing sites which need to be addressed at a national level.
"Helicopters used for search, rescue and emergency medical services play a vital role, but it is essential that the risks associated with helicopter downwash are understood and well-managed.
"The investigation has raised awareness of this issue and been a catalyst for important safety action, which has been taken to mitigate the immediate risk."
The AAIB report said a helicopter had picked up a casualty near Tintagel in Cornwall before flying them to Derriford for treatment.
'Publicly accessible locations'
During the helicopter's "approach and landing" at a "secured area" in a public car park on the hospital site, "several members of the public in the car park were subjected to high levels of downwash".
The investigation said the people who suffered "fatal and serious injuries" were "blown over by high levels of downwash" while in "publicly accessible locations near the Helicopter Landing Site".
It said people were not "prevented from being present" in areas around this site.
The AAIB said following this accident, safety action was taken by the helicopter operator, Derriford Hospital and NHS England Estates "to control and mitigate the risk".
Additional action by Derriford Hospital and NHS England Estates to improve safety is "either planned or in progress", it added.
Contributory factors identified by the report included the fact Derriford's design did not "adequately address the issue of helicopter downwash", while the risk of possible injury to uninvolved people "was not properly assessed".
It said although "a number" of downwash complaints and incidents had been investigated by Derriford, and actions taken, this work did not identify the need to manage "the hazard in Car Park B".
Among other factors was "ineffective communication" between helicopter operators and Derriford Hospital.
The report made nine recommendations to "ensure the protection of uninvolved persons from helicopter operations at hospital helicopter landing sites across the UK".
Plymouth Hospitals NHS Trust said: "We are very sorry that this tragic incident happened and our sympathies go to Ms Langan's family and everyone affected."
It said it had supported the AAIB investigation and made "immediate changes to the operational running of the helipad".
It said in March 2022, aircraft heavier than 5 tonnes (5,000kg) could no longer use the helipad, while the adjacent car park was closed, with increased signage in the area.
It noted national recommendations by the AAIB and said it would work with national bodies to implement them in Plymouth.