Product review (1 stars): Unsafe
The DX8 is an attempt by Spektrum to evolve their beginner line of radios into a more intermediate demographic.  It failed miserably.  The radio was released with a cornucopia of unsafe hardware and software defects, flaws, and legacy design faults.

Do a web search for "dx8 problem" and check out the DX8 owner survey that comes up.  46% (of nearly 500 polled) have unsolvable problems.  That poll is from a Horizon Hobby sponsored website, so it's probably too optimistic.

My own DX8 was such a basket case, it was morally unsalable on the secondary market.  Horizon replaced defective parts with brand new defective parts, like 4 of 4 defective control-stick potentiometers.  In fairness, I own several Spektrum DX6i's, a DX5e, a DX4e and at least 10 entry level UM transmitters and none have had a bad flight control potentiometer.  It's not just me, the internet is overflowing with reports of DX8 problems.  Search around.

A second critical problem is that all Spektrum receivers still use a legacy design that can only draw left-over electrical power from the 5V servo bus, and cannot pull it's own power directly from a high voltage motor battery.  That is because the design has not been updated since the days when all RC planes/helis had internal combustion motors and so servos and receivers had their own low voltage battery.

That's a dangerous design to use with modern e-power'd RC aircraft, because newer digital servos (a must for precise high quality control) and newer accessories like servo-less retracts use a ton of electrical power that can easily, very easily, brown out the servo bus and crash a plane with an old fashioned Spektrum receiver.  Helicopters are bigger, more digital, and even more of a problem to fly with Spektrum radios.  You can mitigate the brownout problem by purchasing a Pro BEC for each one of your airplanes and helicopters.  At $40 a pop, that gets expensive, and there is no guarantee that a Pro BEC will prevent a brownout (for example if a servo or retract gets stuck).

Spektrum's own receiver instructions say, "Inadequate power systems that do not provide the necessary minimum voltage to the receiver during flight have become the number one cause of in-flight failures."  Ok, so why not fix the design??  And what they don't say, is that safe receivers like Hitec's (no affiliation) 36V receivers connect directly to an high power electric plane or helicopter motor battery (up to a 10-cell).

A third problem is that voltage telemetry is built-in to the DX8, but not to Spektrum receivers, so you have to add a $55, 1 once telemetry module to every single model so you know how many electrons you have in the gas tank.

As someone who flies a lot of 3-cell to 12-cell planes and helis, I got REALLY sick of completely uncontrolled crash after crash...

AVOID!!

Buy an Aurora 9 instead.  It is three to five times the radio and commonly sells for less.