Leeham News and Analysis
There's more to real news than a news release.
Bjorn’s Corner: Aircraft stability, Part 9
By Bjorn Fehrm
June 8, 2018, ©. Leeham News: In the last Corner we discussed how a pilot uses the advanced Automatic Flight Control System (AFCS) on modern high-end business jets and airliners.
Now we will discuss what separates the high-end (and expensive) systems from the less capable we described before. It’s about flying difficult routes which contain demanding takeoffs and approaches.
Figure 1. A challenging approach where RNP based navigation is needed. Source: Wikipedia.
Bjorn’s Corner: Aircraft stability, Part 8
By Bjorn Fehrm.
June 1, 2018, ©. Leeham News: In the last Corner, we discussed the how the Flight Management System (FMS) is the part which calls the shots in a high-end autopilot (or Automatic Flight Control System, AFCS, as it’s called in high-end business jets and airliners).
Now we will dig deeper into what happens once the FMS has figured out how we shall follow a route.
Figure 1. The Automatic Flight Control System (AFCS) panel of the CSeries (surrounded with red). Source: Bombardier. Read more
Bjorn’s Corner: Aircraft stability, Part 7
By Bjorn Fehrm
May 25, 2018, ©. Leeham News: In the last Corner we discussed the autopilots one finds in Airliners and high-end Business jets. We looked at how the autopilot was part of the larger Automatic Flight Control System (AFCS) in Bombardier’s CSeries.
To understand how such an advanced system works, we need to go through the different parts of the system and understand their role when the aircraft is flown by the autopilot. We will start with the Flight Management System (FMS) this week.
Figure 1. The flight deck part of a classical FMS (Flight Management System). Source: Esterline.
Bjorn’s Corner: Aircraft stability, Part 6
By Bjorn Fehrm.
May 18, 2018, ©. Leeham News: In the last Corner we discussed the autopilots one finds in Turboprops and entry-level Business jets. Our example was the autopilot for the Garmin G1000 integrated flight deck.
Now we will step up to the airliner level. We will look at the autopilot and its supporting avionics for the Bombardier CSeries. This is a modern, state of the art system, and a good example of the autopilots for an Airliner or top of the line Business jet.
Figure 1. The CSeries flight deck. I have marked the autopilot panel with a red border. Source: Bombardier.
Bjorn’s Corner: Aircraft stability, Part 5
By Bjorn Fehrm
May 11, 2018, ©. Leeham News: In the last Corner, we discussed more capable autopilots used in general aviation aircraft and the Attitude and Heading Reference System (AHARS) we needed to go to more advanced autopilots.
We will now discuss the more advanced autopilots one finds in Turboprops and entry-level Business jets.
Figure 1. The Garmin G1000 Flight deck. Source: Garmin.
Bjorn’s Corner: Aircraft stability, Part 4
By Bjorn Fehrm
May 4, 2018, ©. Leeham News: In the last Corner, we discussed basic autopilots used in general aviation aircraft. The key components for such a system are shown in Figure 1.
Now we will go to more advanced autopilots. We will start with describing the sensors such autopilots need.
Figure 1. The S-TEC 30 roll and pitch two-axis autopilot. Source: Genesys.
Bjorn’s Corner: Aircraft stability, Part 3
By Bjorn Fehrm
April 27, 2018, ©. Leeham News: In the last Corner we discussed the problems with the long term stability of an aircraft. The aircraft deviates gradually in pitch, roll and in a combined yaw and roll mode if left without pilot input.
To hand fly such an aircraft on long routes is tiresome (been there, done that). For these occasions, one needs an assistant, an autopilot.
Figure 1. Simple one-axis autopilot for small aircraft. Source: Genesys S-TEC.
Read more
Bjorn’s Corner: Aircraft stability, Part 2
By Bjorn Fehrm.
April 20, 2018, ©. Leeham News: In the last Corner, we discussed how to stabilize an aircraft in pitch so it could fly stably straight ahead. For this, we needed a horizontal tail which had a negative lift.
This will buy us a short-term pitch stability, but not a long-term one. Why we will explain in this Corner.
Figure 1. The long-term pitch instability, Phugoid. Source: Leeham Co.
Bjorn’s Corner: Aircraft stability
April 13, 2018, ©. Leeham News: In the last Corner we discussed the pressure distribution on a conventional airfoil and compared it with a modern Supercritical airfoil. The Supercritical airfoil (which is used on all modern airliners) achieves a higher cruise Mach and a lower transonic drag by accelerating the air over the wing to a lower supersonic speed than conventional airfoils.
What conventional and supercritical airfoils share is a pressure distribution making them unstable. We need to stabilize them on an aircraft.
Figure 1. The primary forces on an airliner. Source: Leeham Co.
Bjorn’s Corner: Aircraft lift, Part 3
By Bjorn Fehrm
April 06, 2018, ©. Leeham News: In the last Corner, we discussed the pressure distribution of an aircraft’s wing when producing lift. This was with a conventional airfoil (though of the more laminar flow type).
Now we continue by looking at how a modern airliner wing achieves lift by using a “supercritical” airfoil.
Figure 1. The airliner using the wing profile we study, the Emb145. Source: Embraer.