Emergency Landing Dynamic Loads
We will try to understand what it means for interior structures other than seats, in terms of emergency landing dynamic loads. In this post we will dig into the next regulation, 14 CFR Subpart C Section 2-562.
Click here to access pdf versions of the latest blog posts…
§ 25.562 - Emergency Landing Dynamic Loads
In the previous posts, we looked at:
- 14 CFR Subpart C Section 25-301: Loads
- 14 CFR Subpart C Section 25-303: Factor of Safety
- 14 CFR Subpart C Section 25-305: Strength and Deformation
- 14 CFR Subpart C Section 25-307: Proof of Structure
- 14 CFR Subpart C Section 25-365: Pressurized Compartment Loads
- 14 CFR Subpart C Section 25-561: General Emergency Landing Ultimate Loads
14 CFR Subpart C Section 25-562 provides guidelines on emergency landing dynamic loads specifically related to seats, all kinds of seats such as passenger seats, FA seats, and even jump seats (these are flip up cushion seats attached to interior monuments used by flight crew).
Emergency Landing Dynamic Loads - Interiors Structures Related Stuff
OK, this regulation pretty much deals exclusively with seats, their attachments to the seat track floor structure, their dynamic test conditions for certification etc.
So what does this have anything to do with the other monument structures such as bulkheads or partitions/dividers or galleys or lavatories?
It does have an indirect impact. Let us examine these impacts below.
Monument Stiffness and Head Injury Criteria (HIC):
The regulation specifies the load factors and testing requirements for seat certification. And these tests are dynamic tests. The seats are accelerated to 16G and then brought to a total stop as specified in the regulation within a specific time period.
If you cannot see the video above, click this link: Emergency Landing Dynamic Loads Seat Test Video
Generally, anytime there is a monument in front of a row of seats, the common practice is to maintain a gap that is large enough that the test dummy head misses it completely.
But when this is not possible for whatever reason, then the stiffness of the monument in front of the seats becomes important. This is because the test must simulate the contact between the test dummy head and the monument structure in front of it, to meet the stringent HIC criteria for certification.
As we can see in the video above, passenger seats only have the waist harness. The dummy head is moving and basically hits the knees. But if it is obstructed by a windscreen or a partition for example, then the HIC number due to the emergency landing dynamic load test requirement may be too high to certify the seat and the layout of passengers (LOPA).
This dynamic load may also need to be considered as a separate load case if other load cases are not as critical to certify that monument.
Flight Loads for Jump Seats:
From the Ultimate Loads post, we know that there are certain load cases that are specific to in flight turbulence, for example the 6.5G DOWN flight load case.
Jump seats are not supposed to be used as TTL seats, meaning they are not allowed to be used for Taxi Takeoff Landing (TTL). And they do not have any seat track attachments like normal TTL seats do.
Therefore, emergency landing dynamic loads are not applicable. However, the DOWN flight loads are significant, especially considering the weight of the crew member and the seat weight itself.
Typical weight that is used for jump seat certification is 220lb which includes the FAA dummy weight of about 170lb and roughly 50lb for the seat installation. But some DERs may allow a lower weight based on their own experience.
So why are we talking about flight loads all of a sudden?
Because there is a tangent effect that needs to be considered for jump seats attached to monuments.
Just like the seat belts, the jump seats and attachments are also required to be certified for severe wear and tear factor of 1.33, due to frequent in flight use.
Although not common, some DERs may require that this factor be extended to the monument structure attachments (such as floor fitting installations) to the aircraft structure under this jump seat. So keep this in mind and do not be alarmed if it happens to you, you heard it from me, 🙂
Aircraft Structures Modeling Course
If you liked this post, why not share it?