As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF FROM LNK, NOTICE BURNING ODOR IN COCKPIT WITH POWER AT OR ABOVE 70 PERCENT AND APU OFF, ACCOMPLISHED AIR TURNBACK TO LNK. INVESTIGATED AND FOUND WATER SOCK AREA CLEAN AND FREE OF ODOR PER CESSNA 560XL MM CHAPTER 21-50-00, SYSTEM OPS CHECKED OK. RAN AIRCRAFT ON GROUND AT DIFFERENT POWER SETTING AND COULD NOT DUPLICATE STRONG ACID ODOR.