H 4 Aerospace

H4 Aerospace Ltd is an aircraft modification design organisation with its head office on Queensway in Hemel Hempstead, Hertfordshire. It operated as an EASA Design Organisation Approval (DOA) holder for close to 20 years and, since Brexit, has held UK CAA Part 21 Subpart J approval UK.21J.0087. Its senior engineers hold CAA Compliance Verification Engineer status in both mechanical and electrical disciplines.

The company employs up to 25 engineers and support staff across the UK. Its approval covers most modifications needed by airline and VIP operators, and it works with airlines and completion centres. Clients can use H4 for a single project, as an on-demand extension of their own engineering department, or as their main design team, with engineers on site or working from the H4 office. Support engineers can also attend while a modification is installed.

Its avionics and electrical work includes cockpit power for electronic flight bags, in-seat AC and USB power, and electrical support for galleys, toilets, defibrillators and cabin reconfigurations. It designs in-flight entertainment, Wi-Fi, airshow and SATCOM systems, as well as EGPWS, TCAS and Mode S installations, ADS-B Out to CS-ACNS, and communication and navigation upgrades.

H4 has also worked on programmes certified by the FAA, Transport Canada, Brazil’s ANAC and other authorities.