# Tag Info

## Hot answers tagged empennage

7

It's a "bullet fairing". Sometimes you get the pressure fields of the vertical and horizontal surfaces in alignment so the lowest pressure zone of the vertical fin is merged with the lowest pressure zone of the horizontal tail right at the intersection of the surfaces. It results in a more extreme pressure recovery aft and can cause flow separation and ...

5

"The sweepback angle of the horizontal stabilizer is greater than that of the wing." Usually it has to be about 5° higher as the the Wing so the critical Machnumber is higher for the Empennage. You dont wanna lose efficiency due to shock waves on the tails (tails have always to work). There are also rules for the thickness and other parameters of ...

4

Well, it's the same reason that the Challenger ultralight demonstrates extreme "adverse yaw" in response to aileron inputs when flown with the doors on, but less so when flow with the doors off. The floats-- like the doors-- increase the surface area in front of the CG, which has an effect similar to decreasing the size of the vertical fin (which, ...

4

It seems the dorsal fairing is already made of composite materials. See the images below. These components only receive aerodynamic loads and maybe unlikely yet possible foreing object impacts. (taken from this paper) (from google with "atr 72 tail fin fairing" keywords) From the below picture (from here) you can easily spot aluminium components ...

4

The loads on section of a dorsal fin are minor, just from the dynamic pressure of airflow that may be striking the panel from the side during yaw excursions in turbulence. It's a "lifting" surface, insofar as it's contributing to the restorative yaw moment being part of a stabilizing fin, but the loads aren't super high and it may even just be ...

3

In some aircraft, that protruding spike houses the high frequency comm antenna and its tuning mechanism. In others it contains parts of the elevator angle-of-attack control mechanism.

3

In airplane empennage design, there is a thing called Tail Volume Coefficient. Mind you, there are no volumes here, but you are working with $m^3/m^3$. It is calculated as follows: Horizontal tail volume: $V_{HT} = \cfrac{ l_{HT} \cdot S_{HT} }{ c_{REF} \cdot S_{REF} }$ Vertical tail volume: $V_{VT} = \cfrac{ l_{VT} \cdot S_{VT} }{ b_{REF} \cdot S_{REF} }$ ...

2

Tail volume has very little to do with CG, and it is rather silly to have it so far back that the tail has to lift. Unless there is a specific reason to put CG at 50% chord, put it at 25% for starters. You can always move the CG. Tail volume (specifically horizontal) is there as needed not only for trim in flight, but also for directional stability and ...

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