on his Casualty Card visible online the Aircraft Serial that Sullivan died in was HP "D8807" As this was an Avro 505K Serial I think should be D8307
Westall died 30th later as a result of injuries received in flying accident which looks like occurred on 29th
The Incident Card has the crew of HP "D8807" as 2 Lt L H Sullivan (Pilot), 2nd Lt A Westall (Observer) and AC1 G W Tucknott #227228 Injured and location as 'France'
All 216 Sqn
See for yourself
http://www.rafmuseumstoryvault.org.u.../raf_vault.php