# Are there commercial airplanes that are still flyable without any electricity? [duplicate]

This question already has an answer here:

I have seen the first episode of Revolution yesterday and there are all kinds of airplanes just falling from the sky because of complete loss of electricity.

I know most if not all modern planes use fly-by-wire systems.

I thought about this and the the question occurred:

Are there any still commercial airplanes in use that are still flyable with complete loss of all electric systems?

Do some commercial airplanes still have mechanical backup mechanisms to manoeuvre?

## marked as duplicate by RoboKaren, mins, Danny Beckett, HDE 226868, foootMar 31 '15 at 20:46

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

• Why did electric systems fail? Also, the best-selling jet airliner in history (the 737) is not FBW, so it's not even "most" airliners that are FBW -- among Airbus and Boeing, it's just A320 and beyond for Airbus and 777 and beyond for Boeing. @mins It's certainly possible, but anything that causes it likely leads to even bigger issues. – cpast Mar 31 '15 at 6:30
• My best advice to you is to believe nothing you see on TV, especially mini-series like this. Let's just say that they have a poor record for accuracy, especially on anything to do with aviation. – Simon Mar 31 '15 at 7:04
• @Simon Anything to do with technology at all, for that matter. – reirab Mar 31 '15 at 14:10
• @Simon, the lack of knowledge and accuracy of technical information on tv is so bad I am beginning to not trust them for eavin information within their specialty: making video. – hildred Mar 31 '15 at 14:18
• Buffalo Airways still operates at least one DC-3 in passenger service - the flight controls on that aircraft are entirely mechanical (cable and pulley) with the exception of the wing flaps, cowl flaps, and landing gear/brakes. Probably not the answer you were looking for though... – voretaq7 Mar 31 '15 at 16:13

## 2 Answers

Are there any still commercial airplanes in use that are still steerable with complete loss of all electric systems? Do some commercial airplanes still have mechanical backup steering mechanisms?

Yes and Yes.

On most(*) Airbus aircrafts,

In case of a complete loss of electrical flight control signals, the aircraft can be temporarily controlled by mechanical mode.

This is called MECHANICAL BACKUP and is the lowest level of control law (after Normal, Alternate and Direct Laws)

The aircraft can be steered:

• Pitch control is achieved through the horizontal stabilizer by using the manual trim wheel.
• Lateral control is accomplished using the rudder pedals.

The pilots are notified with:

A red MAN PITCH TRIM ONLY warning appears on the PFD.

But:

Both controls require hydraulic power.

This means that if the aircraft looses BOTH electrical and hydraulic power, is no more controllable.

Usually there are pressurised hydraulic reservoirs that allow to have a minimum of hydraulic power even if there is total loss of electrical power, but if there is substantial damage to the aircraft that has severed the hydraulic lines, this is no more applicable.

(*): beyond the A320. Functionalities vary in the following manner: (emphasys mine)

Primary Flight controls:

Back-up Control Logical evolution of A320 / A340 / A340-600 family:

Full Fly-By-Wire, with a “Back-up” as an additional precaution to keep control of the aircraft during temporary loss of:

• all Primary Flight Control computers
• all Electrical power supply

A320 : full FBW controls, mechanical Back-up (Pitch Trim & Rudder)

A340/A330 : like A320, additional Yaw Damper to improve Dutch Roll damping even in Back-up mode (BYDU with hydraulic micro generator)

A340-600 : like A340 for pitch, Rudder becomes fully Electrical (BPS + BCM : Back-up Power Supply + Control Module)

A380 : like A340-600 for Yaw control + BPS+BCM also power:

• Electrical Pitch Back-Up (elevators) linked to side-stick
• Electrical Roll Back-Up (ailerons) linked to side-stick
• Pitch Trim (Wheel is replaced by Switches)

For the A380, in particular:

Active Stability Control functions:

All levels of control laws (Normal, Alternate, “Direct” and even Back-up) include a Yaw and Pitch damping function

It's not even true that most airliners use fly-by-wire. Among Airbus and Boeing models, the A320 and beyond use FBW on the Airbus side (note that the A300 was produced until 2007), and the 777 and beyond use it on the Boeing side. This is probably a majority of major commercial aircraft, but it's by no means a vast majority.

Among these aircraft, virtually all of them have a backup to the electrical system. On most Airbuses, there is a mechanical backup (which directly triggers certain hydraulic control surfaces); only on the A380 is this absent. The Boeing 777 and up have FBW, but the 777 also has a mechanical backup.

In addition, the 737 (one of the most common aircraft worldwide) has pure mechanical reversion -- it's controllable even with total loss of hydraulics, let alone electricity.

• Very interesting, I didn't know this. Thank you. – EvilFonti Mar 31 '15 at 6:56
• Mostly controllable even with total loss of hydraulics - the 737 has full mechanical control capability for the ailerons and elevator, but limited mechanical rudder control (although, IIRC, this is due to the large amounts of force necessary to overpower the large aerodynamic loads on the rudder, rather than any inherent limitation of the rudder controls). – Sean May 2 '18 at 15:19