Landing

Gulfstream GVII

Eddie sez:

Last revision:

2020-08-06

AFM Procedure

[AFM, §02-05-50]

    NOTE

    When approach guidance is established on final approach, a subsequent deviation may not recapture in a timely manner unless the approach button is rearmed.

  1. SEAT BELT / NO SMOKE PASSENGER WARNING . . . ON
  2. CAUTION

    THE SPEED BRAKE HANDLE MUST BE FULLY SEATED IN THE RETRACT DETENT TO PREVENT INADVERTENT EXTENSION.

  3. LANDING GEAR / Lights . . . DOWN / 3 green
  4. WARNING

    FLAPS MUST BE SET AND EXTENDED TO 20° PRIOR TO SELECTION OF FLAPS TO DOWN.

  5. FLAPS . . . DOWN
  6. WARNING

    APPROACH SPEED IS VREF + 5 KNOTS; HOWEVER, IN STRONG WIND CONDITIONS, ADD TO VREF 1/2 OF THE STEADY STATE WIND PLUS THE GUST INCREMENT TO A MAXIMUM ADDITIVE OF 20 KNOTS. APPROACH SPEED, INCLUDING ANY GUST ADDITIVE SHALL BE MAINTAINED TO THE THRESHOLD AND SHALL BE USED TO DETERMINE LANDING DISTANCE.

    Notice this is no longer a recommended technique, it is procedure. So how do you do this? See VREF Additive, below.

  7. Approach / Landing Airspeeds . . . Verify

  8. CAUTION

    AFTER TOUCHDOWN, PEDAL STEERING AND / OR RUDDER AERODYNAMIC CONTROL SHOULD BE USED TO MAINTAIN DIRECTIONAL CONTROL. DIFFERENTIAL BRAKING SHOULD AUGMENT PEDAL STEERING AS RUDDER EFFECTIVENESS DECREASES (IF REQUIRED). CONSIDER LIMITING T/R USE IF LANDING SURFACE IS DEGRADED OR CONTAMINATED TO PREVENT AIRCRAFT DAMAGE.

VREF Additive

You must make the VREF additive called for by the AFM, it is no longer optional. This is a two step process. First, you have to make sure you have enough runway for the additional speed crossing the threshold. Second, you need to fly it. Fortunately, both of these steps can be done with a few key presses.

Step One: Do I have enough runway?

From the TSC FMS page select the "Perf Landing" page and enter the additive to the Threshold speed and Confirm Init to LDG Data. The computed landing distance will include this speed additive to your landing distance.

images

Photo: GVII Touch Screen Controller Perf Landing Page, with a 5 knot VREF additive
Click photo for a larger image

This automates the process of assuming you will be crossing the threshold with all of the additive so you can be assured you will still have enough landing distance. Many of us have been doing this manually for years. See: Gust Additives.

Step Two: Fly the Additive

From the TSC FPLN page select "Flight Progress" and then "Departure and Approach Speeds" and enter the additive. The auto-throttle speed target will adjust automatically for you once you select the Flaps Down (39°) and will hold that until crossing the threshold.

images

Photo: VREF additive on TSC
Click photo for a larger image

In previous Gulfstreams we would MAN SPEED the target and you can do that with this airplane too, but don't. Keeping auto speeds will make a go around easier (one less button to remember).

Technique

[Ground and Flight Operations, pp. 243-244]

Normal Landing

    NOTE

    Minimum disengage height for the autopilot is 90 feet AGL from an ILS or LPV Approach (Flaps 39°), 130 feet AGL (Flaps 0°, 10°, 20°) and 200 feet AGL for all other operations. Maximum demonstrated altitude loss for coupled go-around is 50 feet. For limitations concerning use of the autopilot, see Section 01-22-20, Autopilot.

    We are told that you can go lower with Flaps 39° because you will be at approach idle and not flight idle. I'm not so sure, according to the PAS, pp. 14-16 to 17, flight idle occurs with the gear up and flaps <22° while approach idle requires the gear down or flaps >22°. More about this: GVII Powerplant.

  • The best landing technique involves a power reduction to IDLE at 100 feet, to cross the runway threshold (50 feet AGL) at VREF. Then allow the aircraft to fly onto the runway, after a gentle flare, with a shallow sink rate. As the aircraft approaches touchdown, ground effect will further reduce sink rate and produce a smooth touchdown with very little additional back pressure on the sidestick. There is no need to “hold off” to produce a smooth landing.
  • I don't agree with this technique. If you are at 100 feet on the correct glide path at VREF+5 and begin a power reduction, the airplane will lose more speed than the 5 knot additive or you will dip below glide path. Note this is above the height where ground effect takes effect. But even if you cross the threshold at VREF at the correct glide path, you will certainly dip below or go below VREF. This "best landing technique" has been preached by Gulfstream for a while now and I've noticed pilots tend to dip down into ground effect and then float, looking for the soft touchdown. I believe you can fly the airplane onto the runway using the autothrottle "Retard" function and end up in the touchdown zone and on speed.

  • The G500 wing produces considerable ground effect. Approach speeds above VREF+5 and/or a late power reduction to idle will exacerbate ground effect and could result in touchdown beyond the touchdown zone.
  • Ground effect will only cause the exacerbated effect if you allow it to. The airplane should cross the threshold between 500 and 700 fpm, depending on approach speed, glide path angle, and winds. Allowing that to continue until 20 feet preserves the downward momentum.

  • At touchdown, the PF will gently lower the nose to the runway and, as necessary, deploy the thrust reversers and apply brakes to slow the aircraft. If the PF briefs use of the thrust reversers, the PM will confirm thrust reverser deployment. If one or both thrust reversers do not deploy, the PM will state “No Thrust Reversers”. As the aircraft approaches 70 KCAS, the PF will begin to reduce reverse thrust to idle reverse by 60 KCAS. Rudder and rudder pedal steering are the primary means for steering during rollout. Ensure the aircraft has slowed to a safe taxi speed before turning off the runway.

  • Performance landings target 4-6 ft/s touchdown sink rate to meet published landing distance data.

Crosswind Landing

  • The maximum demonstrated crosswind component for takeoff and landing is that component of crosswind that was demonstrated to the FAA during certification testing. For the G500, the maximum demonstrated crosswind was 33 knots.

  • During the final approach phase of the crosswind landing the pilot should fly aligned with or slightly upwind of the runway center line utilizing crab into the wind sufficient to stabilize the aircraft in drift. Due to the varying crosswind components, the pilot must adjust the crab-angle, as required, during the descent on the approach path. Avoid excessive airspeeds during the approach. A prolonged float after flare will increase pilot work load during touchdown. Drift correction during touchdown is far easier when the pilot can control the timing of the touchdown.

  • Approaching touchdown, the rudder is applied to align the aircraft fuselage with the runway and simultaneous opposite aileron is applied to achieve zero drift. This combination of wing down/opposite rudder should be coordinated throughout the final portion of the landing approach until touchdown. Touchdown with the upwind landing gear first, then set the opposite main wheel on the runway without delay. Utilize the rudder as needed to keep the airplane on the runway centerline. Use aileron into the wind as necessary to keep the upwind landing gear on the runway. Immediately after touchdown lower the nose wheel to the runway in a smooth manner. As the roll out speed decreases, the pilot will be able to maintain the centerline with pedal steering and normal braking. Continue to apply aileron (stick) into the wind for best results. The use of thrust reversers is the pilot’s option, but be aware that in crosswinds and icy runways, the thrust reversers are destabilizing below approximately 80 knots. Do not deploy the thrust reversers at the expense of maintaining the airplane down the runway centerline. For landings on wet or icy runways, the maximum recommended crosswind is reduced as indicated on the maximum allowable crosswind chart.

Braking

I have long had a philosophy that the sooner you get the airplane to 80 knots, the better. When things go badly, you are better off at taxi speed than landing speed. But I also think hopping on the brakes to make an intersection after landing may be putting too much stress on the airplane and can even reduce directional control, so there is a balance to be had. The GVII autobrakes have been a game changer. I was warned that overriding the autobrakes took a lot of practice to do smoothly but I simply used my old Boeing 747 technique and things went well from my very first landing in the airplane. That technique: let the autobrakes do their thing until 80 knots, then apply just enough pressure to override and then maintain that pressure until you can reduce it. Easy.

Over the following months we started getting more and more aggressive to the point we were overriding almost immediately after touchdown and our braking became jerky. See: Smoothness for more about this aeronautical engineering concept. So then we thought, why wasn't this a problem before? Our solution: back to the basics:

image

Technique: Let the autobrakes do their thing until 80 knots, then apply just enough pressure to override and then maintain that pressure until you can reduce it.



Here is a video of our very next landing: GVII Autobrake Technique. I took time stamps of the video while looking at the airspeed on the PFD. We touched down at 121.5 knots and got to 80 knots 7.96 seconds later on autobrakes alone, using the Medium setting. That comes to a deceleration rate of 5.21 nm/hr per second, and that comes to:

5.21 nm hr 6076 ft nm 1hr 3600sec =

8.8 ft/sec2

This is a little less than the advertised autobrakes medium rate, but remember the autobrakes ramp up to that rate over three seconds.


Gulfstream GVII-G500 Airplane Flight Manual, Revision 5, March 3, 2020

Gulfstream GVII-G500 Ground and Flight Operations, released as part of the GVII-G500 AOM, §02-01-10

Gulfstream GVII-G500 Production Aircraft Systems, Revision 3, July 15, 2019