Pegasus Airlines Boeing 737-800 TC-CPF overrun runway at Trabzon. All pax okay

[A0283]

Grossly simplifying it ...and in general ... Inop is allowed because the thrustreversers are technically an 'extra'. Operationally you could/should be able to do without them. You might take a look for example at how required landing distances are calculated for each flight.

You might say that is from a safety point of view. But add to that that a 'braking' backup is 'nice'.

From an operational point of view there are advantages in 'taking an exit earlier'.

With Murhpy in mind you might say that every added feature creates added types of errors, incidents and accidents. That is true for basic and safety features. Like an ELT (battery) malfunction burning a hole through a 787 fuselage. Or an escape slide inflating inside the cabin and blocking an exit.

So Murphy is not surprised that a reverser inop with a potential asymmetry can lead to an actual asymmetry event. In spite of the multiple layers of defensive safeguards.

Overall the balance is positive, thats why they are on, and why you are allowed to fly with one locked under specified conditions and procedures.

Again, grossly simplified, but hope it gives an idea about some of the factors involved.