Date: 201604
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Light: Night
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
Aircraft component: Cargo Restraint/Tie Down
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Training / Qualification; Situational Awareness; Distraction; Communication Breakdown; Workload
Second reporter function: Captain
Anomaly: Deviation / Discrepancy - Procedural Weight And Balance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Ground Personnel
When detected: Pre-flight
Result: Aircraft Aircraft Damaged; Flight Crew Took Evasive Action; General Release Refused / Aircraft Not Accepted
Contributing factors: Aircraft; Company Policy; Procedure
Primary problem: Company Policy

Narrative: During preflight; Crew Chief alerted us to damage in rear cargo hold caused by awkward and heavy metal cargo. Weight was approximately 1;260 pounds in total; or approximately 210 pounds per item (6 items total). The aircraft was taken out of service due to damage.Cargo was six small pallets each containing one large metal cylinder. Unknown circumstances caused one of these pallets to damage the floor of the rear cargo hold. Upon investigation by the First Officer (FO); it was learned that this cargo was not able to be anchored into the cargo hold; and was placed far aft of the aircraft.My concern as the flying pilot (FO) would be this cargo shifting rearward during takeoff roll and discovered upon reaching Vr. TPS called for Flaps 1 configuration; which allows for the least amount of clearance between the underside of the tail and the runway. Should the cargo have shifted aftward during takeoff/rotate; it could have caused a tailstrike; damage to the pressure bulkhead; lavatory storage; or other cargo. While unlikely; it could have caused excessive aft CG; thus presenting potentially catastrophic flight control issues.Secondly; upon assignment to new aircraft; the captain specifically notified dispatch that he was refusing the cargo for. I was a witness to this.  We were assigned another aircraft in a different concourse. I notified the crew chief at the new gate about the issue and to not load the cargo should it arrive. He was aware and assured me it would not be loaded; per captain's orders. Approximately 20 minutes later; the crew chief notified me that the cargo did show up at the gate for loading and that he had refused it. I went outside to take pictures of the cargo to document the matter. Offending cargo was taken away and its disposition is unknown to me. B737s do not have sufficient mechanisms for securing heavy; dense; or awkward cargo. There are no floor locks; containers; sufficient cargo nets; etc. The 737 is designed to carry passenger luggage; mail; standard air freight; some AOG parts; etc. Had we not been alerted to the cargo (had it been loaded without incident); and the cargo shifted rearward on a FLAPS 1 takeoff; I fear a tailstrike would have been likely.  The spring-loaded narrative during the history of passenger air travel is to blame the pilot first; last; and at every point in between for any aircraft mishap. Unless there is a manifestly obvious cause to counter the pilot error narrative; the pilot is left to defend his career and reputation with little evidence to support himself. In this incidence; I fear the shifting rearward of such cargo would have been attributed to improper pilot takeoff technique; rather than the shifting of the cargo causing unforeseen control issues. The captain and I (with a combined 47 years of service to the Company) would be to blame; not the cargo loading.  There is no procedural mechanism to capture such a loading error. The preflight walkaround does not include the FO opening the cargo compartments and inspecting the cargo; nor does it include weight and balance calculations. For issues such as this; the crews are at the mercy of the competence of the load planners and ground crews.Limit the types of cargo taken in smaller passenger aircraft. Heavy; awkward; or dense cargo can't be secured. If so; they should not be put in the aft cargo for obvious reasons. Control issues are the primary concern; but aircraft damage is also at issue.I would also like for a simulation of this to happen and see what happens to the 737-800 if the cargo shifted in the aft cargo hold at rotate. If the Company wishes for me to participate; I am willing to do so; but only if I am taken off an existing trip with pay.


Second narrative: These over 200 pound hubs were strapped (insecurely) on individual tiny pallets. There were six of them I believe. They had to be top heavy in my opinion. Packaging cargo is not my expertise but if they had been properly secured on a larger pallet and placed in a cargo compartment other than the aft compartment; this may have not been a problem.


Synopsis: A B737-800 aft cargo compartment floor was damaged after six 210 pound unsecured pallets were placed in it. The crew was additionally concerned about the unsecure cargo shifting at Vr. The pallets were removed and the aircraft taken out of service.