Mechanical HSI vs EHSI
 

Thoughts please: our scenario, changing from SPIFR helicopter with 4-axis AP interfaced to EHSI to a SPIFR BK117 with 3-axis AP and mechanical HSI.
We had planned to replace mechanical HSI's with Sandel 4500 EHSI, some say don't bother, don't need EHSI and might upset AP interface with original factory fitted avionics. But we like auto-slave of an EHSI for reducing work load eg. IMC windy turbulent night 90degree course changing approaches. What say you all please???:hmm: