A desperate MechWarrior piloting a jump-capable 'Mech can literally leap onto his target, bringing the full weight of his machine crashing down on the victim's head. This type of attack, known among MechWarriors as “death from above,” is extremely difficult and always results in some damage to the attacker ('Mech legs were not designed to take this kind of stress), and so MechWarriors rarely attempt it except as a last-ditch measure.
In order to execute a DFA, the attacker must have enough Jumping MP and be able to jump into the hex containing the target. The attacker then literally jumps into the hex containing the target, though it stops just short of that hex until the Physical Attack Phase.
DFA attacks must be declared during the Movement Phase, but like all other physical attacks, they are resolved during the Physical Attack Phase. This means the attacking unit can only attack units that have finished their movement. It also means a unit making a DFA cannot be the target of a charge or DFA, since its movement will not be finished until the end of the Physical Attack Phase.
A 'Mech making a DFA cannot be the target of physical attacks, but may be the target of weapon attacks.

Multiple Attacks: A unit may only be the target of one charging or DFA attack in a given turn.

Submerged Naval Vessels and Aerospace Units: These units cannot be the target of a death from above attack.

Stacking: A 'Mech does not count as stacked in a hex while executing a death from above attack until it completes the attack. As soon as it lands, normal stacking limits apply.

Weapon attack phase The attacking unit cannot make any weapon attacks during a turn in which it is executing a DFA.
During the Weapon Attack Phase, the attacking unit is considered adjacent to the target hex along the path that the attacking unit will travel during the jump, and facing the target hex. If the path of the jump passes exactly between two hexes adjacent to the target, the attacker must choose which one he will occupy. For purposes of determining LOS, the attacking unit is considered to be in the air above the hex, standing one level higher than the target hex or the level of the hex the attacker occupies, whichever is higher.
If the attack is successful, both BattleMechs take damage as determined below. If the attack fails, the jumping 'Mech crashes to the ground and takes damage (see Falls, below).

Falls: If the attacking 'Mech takes damage during the Weapon Attack Phase that forces the pilot to make a Piloting Skill Roll, the player should roll as normal. A failed roll means the attack automatically misses. Resolve the attacker's fall and ending location per the rules below.

To determine damage to the target inflicted by a death from above attack, divide the weight of the attacking 'Mech by 10 and multiply the result by 3, rounding fractions up. For example, a Jenner weighing 35 tons inflicts 11 points of damage.
Divide the damage into 5-point Damage Value groupings. Determine attack direction as though the attack had come from the attacking 'Mech's starting hex, then determine the hit location of each damage grouping by rolling 1D6 and consulting the 'Mech Punch Location Table.

Vehicles: Resolve successful death from above attacks against a vehicle on the Front column of that vehicle's Hit Location Table.

Prone 'Mech: Resolve successful death from above attacks against a prone 'Mech on the rear column of the 'Mech Hit Location Table.

The attacker takes damage as if from a successful attack on its legs. To determine the amount of damage, divide the attacker’s weight by 5. Then divide the result into 5-point Damage Value groupings. Roll 1D6 for each damage grouping and consult the Front column of the 'Mech Kick Location Table to find the hit location.

Location after attack At the end of a death from above attack, the attacker lands in the target's hex. If the DFA is successful, the target is pushed one hex in the direction opposite the attack. If the attack fails, the target chooses an adjacent hex and moves to it, even if immobile or prone. This motion might result in an accidental fall from above or a domino effect or even a Piloting Skill Roll for entering a building hex.
If the target unit cannot be displaced into the appropriate hex (for example, if the terrain is prohibited), the hex chosen must be as close as possible to the original hexside through which the target unit would have moved. For example, if the direction of the attack would have pushed the 'Mech through Hexside A, the controlling player then looks at hexsides B or F to see if those hexes are passable, then at hexsides C or E, then finally at hexside D. If two equally distant hexes, such as B or F, are open, the appropriate player may choose either one, as described above.
If all the surrounding hexes contain impassable terrain, the target unit cannot be displaced. For example, the target ’Mech may be on Level 0 terrain surrounded by Level 3 or higher hills. In this case, if the attack succeeds, the target is destroyed. If the attack fails, the attacker is destroyed.

A successful death from above attack may cause both 'Mechs to fall. Both MechWarriors must make Piloting Skill Rolls, the target adding a +2 modifier and the attacker adding a +4 modifier. If either unit fails this roll, the unit takes damage as from a 0-level fall.
On an unsuccessful attack, the attacker automatically falls, taking damage as though the ’Mech had fallen 2 levels onto its back.