AN ACR FK10 FO DISCOVERED THAT THE RADOME HATCH WAS IMPROPERLY INSTALLED AND HE WAS UNABLE TO INSTALL IT HIMSELF. HE FORGOT TO INFORM MAINT PERSONNEL. THE ACFT WOULD NOT PRESSURIZE AFTER TKOF.

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DURING THE WALKAROUND; I FOUND THE LOWER NOSE RADOME ACCESS HATCH INSTALLED BACKWARDS; SO THAT THE HANDLE COULD POSSIBLY BE BLOWN OPEN BY THE SLIPSTREAM. I REINSTALLED THE HATCH; BUT WAS UNABLE TO GET IT COMPLETELY CLOSED AND LOCKED. I THEN FINISHED THE WALKAROUND; INTENDING TO CALL MAINT. HOWEVER; UPON RE- ENTERING THE ACFT; I ALLOWED MYSELF TO BECOME DISTR WITH SOME OTHER PROBS AND FORGOT TO PLACE THE CALL. AFTER TKOF THE ACFT WOULD NOT PRESSURIZE. I REMEMBERED THE HATCH AND TOLD THE CAPT. WE RETURNED TO ORD; LNDG 4000 LBS OVERWT. MAINT SECURED THE HATCH AND THE OVERWT INSPECTION WAS OK. WE THEN FLEW TO AUS WITHOUT FURTHER TROUBLE. I COMPLETELY ACCEPT THE FULL BLAME FOR MY LAPSE OF ATTN. BUT I HAVE SEVERAL SUGGESTIONS: 1) I FREQUENTLY FIND THE RADOME AND AVIONICS HATCHES INSTALLED BACKWARDS. GND CREWS SHOULD KNOW THE PROPER INSTALLATION. 2) WHILE THERE ARE MFDU ALERT MESSAGES FOR UNLOCKED AVIONICS HATCHES; THERE IS NONE FOR THE RADOME HATCH. PERHAPS THIS COULD BE CHANGED. 3) WHEN GND PUSHBACK CREWS DISCONNECT THE TOW BAR; AS A BACKUP; THEY COULD BE INSTRUCTED TO CHK THE RADOME HATCH ABOVE THE NOSE GEAR. SUPPLEMENTAL INFO FROM ACN 398324: DURING INITIAL CLBOUT WE HEARD A RUSH OF AIR THAT WAS COMING FROM THE NOSE OF THE ACFT. WE ALSO NOTICED THAT THE CABIN WAS NOT PRESSURIZING. I DISCUSSED THAT THERE MIGHT BE A PANEL OPEN. AT THAT TIME THE FO SAID THAT DURING PREFLT HE FOUND THE RADOME ACCESS HATCH WAS PUT IN BACKWARDS. AT THIS TIME; WE WERE LEVEL 5000 FT AND 200 KTS. WE RETURNED TO ORD WITH AN UNEVENTFUL 92000 LB; 100 FT SINK RATE LNDG. I ELECTED NOT TO BURN DOWN TO LNDG WT BECAUSE OF THE UNCERTAINTY OF THE HATCH STAYING WITH US. WE TALKED ABOUT HOW TO AVOID THIS AND THE FO SAID HE WOULDN'T TOUCH THE HATCHES ANYMORE AND JUST CALL MAINT TO FIX IT. ALSO WE NEED TO TELL MAINT HOW TO PUT THE HATCH IN PROPERLY. THIS HAPPENS QUITE OFTEN.