# What's P-Factor and why does it occur?

Steve V.
• What's P-Factor and why does it occur? Steve V.

Whenever I hear anyone talking about P-Factor, (whether it be single-engine left turning tendencies or multi-engine loss of directional control scenarios), someone always brings up the fact that the descending blade of a propeller generates more thrust than the ascending blade. I'm wondering why that's the case.

What is P-Factor and why does it occur?

• Rather than try to do a full ground school session, I'm going to point you at the section on P-Factor in the awesome (free) textbook See How It Flies.

To attempt to paraphrase, it occurs when your aircraft is operating at high angles of attack. Just like the advancing blade on a helicopter produces more thrust because it's heading upwind, the descending blade of the propeller produces more thrust because it has a higher angle of attack relative to the aircraft's motion through the air.

• Just imagine an aircraft is perfectly level and moving forward through the air. The angle of attack on both blades of each propeller would have the same angle of attack. Now imagine the plane pitches up a bit. One blade's angle of attack will increase and other will decrease. Within reason, the greater the angle of attack, the greater the thrust generated. So one blade (or, to be more precise, a blade on one side of the aircraft) will generate more thrust than the other.

Tags
Related questions and answers
• Whenever I hear anyone talking about P-Factor, (whether it be single-engine left turning tendencies or multi-engine loss of directional control scenarios), someone always brings up the fact that the descending blade of a propeller generates more thrust than the ascending blade. I'm wondering why that's the case. What is P-Factor and why does it occur?

• Jet engines are designed to contain a fan blade failure, and the engines and airplanes are designed with this type of failure in mind. This is more critical in the modern high-bypass designs with large fans. Pictures from bird strikes sometimes show pretty severe damage, but I don't remember any that actually lost a fan blade. How often does a jet engine actually lose a fan blade? This is different from a rotor burst, which is uncontained (like with Qantas Flight 32).

• , the controller does not have the altitude of the target. Given this, I conclude that ATC radar does not have the altitude (angle-up) to the target, and only provides azimuth. So then without the altitude, how does the radar-system know where to put the target laterally on the screen? Example, a radar picks up a target that is 10 miles from the station. If the target is 0 AGL, the proper position would be 10 miles out. However, if the target is at 15,000ft, the proper position would be 9.5 miles out. Since the difference is so small, does the radar just put the target at 10 miles, and the FAA separation

• For fun I want to build a flight simulator at home. What are my options from most basic toy environment to more realistic set-up. Great if you can give for each solution a basic indication of cost (software / hardware), and if appropriate the space needed.

• My only detailed experience with carburetors is in aircraft. I'm pretty familiar with the principles behind float-type carbs, but I recently saw a schematic for a "downdraft carburetor" with a choke valve. This got me curious, so I did a little research and found that what I'm used to is an "updraft carburetor", and that (according to wikipedia) they fell out of fashion in the automotive industry in the 1930s. Why is the updraft carburetor design so prevalent in aviation? Does an updraft carb actually have a choke valve? Images below to provide a little context for those of us who

• I was looking through my virtual radar logs one of the days and found this "glitchy" ADS-B behavior. I am almost 100% sure that this is not due to my antenna or setup since two independent different radars confirmed this weird behavior from FlightRadar24. Also A/C before and after this one did not exhibit this behavior. Does anybody have any thoughts as to what may be happening??? Why is the "skew" at seemingly same angle? Is that anything? In light of MH370, does this happen often, how reliable is that GPS data? Tail # N657UA Boeing 767-300 Typical route between EGLL and KORD Time

• I am currently working on the modeling of blade/casing interactions in aircraft engines. The work is carried out in partnership with a company, therefore, there is a limited amount of it that could be published openly. Are there any OpenSource compressor or turbine blade designs available (e.g. NACA airfoil profiles for wings)? Where could I find detailed dimensions and material properties? The idea would be to use it for publication purposes, thus displaying relevant characteristics and realistic behaviors, while keeping all the confidential data of the company internally.

• I'm a low time PPL. In my personal opinion, practice pans, perhaps one or two a year, are a good thing. Practice in a procedure that builds confidence removes one more item from the pucker factor list if it does all go wrong and lets your brain focus on the situation. The D&D cell are always happy to assist and I know that they welcome it as it gives them practice as much as it does me. They are always excellent and it's comforting to know that they are there if I ever need them for real. However, I know that many pro pilots do not approve of this. I am aware that they are often

• With the new Boeing 787 where Boeing has provided the capability to swap engine types if the aircraft goes to a new operator quite quickly, I'm wondering if there are any interchangeable flightdecks... the similarities would make training easier. I know a similar project was done on the DC-10s becoming MD-10s, as well as some Saudi MD-90s to be similar to MD-11, but both of these were long-time consuming projects. But I'm wondering if there are any aircraft which have this possibility and if not, why not? I'd see it as an opportunity to Boeing to have a 787 flightdeck shared with say the 777.

• Last August during a certification flight, a Cessna 182JT-A compression-ignition (diesel) engine failed in flight. I've been Googling to find the cause of the failure and the status of the certification process but have failed to find any recent info. Does anyone know what the current findings have been and how Cessna expects to proceed?

Data information