Wow! I don’t understand why you are attacking over some advice but ok. I fly slower like that as i like to keep the plane leveled during decent not have a nose dive where I have to keep applying spoilers every 5-10 seconds. The decent is also based on a typical vnav decent.
Unless of course it is during descent. M0.8 from FL400-FL350 is typically what speeds airlines cruise with anyways. The deceleration to M0.7 between FL350-FL300 is not all that slow as again you are descending not climbing i didn’t think it was unrealistic. But doly noted.
I thought having flaps 5° was more realistic than having to apply flight spoilers every 5-10 seconds. It is one of the lower flaps settings and is commonly used during takeoffs which pilots typically retract them at about 3,000ft-5,000ft 777s get to 250kts IAS at bellow or about 2,000ft as well. I watched plenty of 777s takeoff IRL so I would know.
So before you attack someone over some false pretenses of what advice you think is realistic or not please learn how to discuss things and explain better without attacking someone or flagging their comment to be removed, just because you don’t agree with their information. If I made a mistake or my information is incorrect please refrain from attacking me and instead explain how my information is wrong rather than assume I am just an unrealistic idiot. Because that I can assure you that I am not.
I’m gonna have to disagree as this does happens IRL tho, and I’ve seen it happen when I’m a passenger looking out at the window seat. The reason you may say its unrealistic is that it’s probably uncommon, but as a traveller, I’ve seen it happen more on slippery aircraft like the MAX or 757
sorry for saying this, but i DO kind of agree it is bad advice (not trying to be mean, just saying here 😅) because this doesn’t happen IRL in any occasion. ALTHOUGH, if you just play Infinite Flight for pure fun and not focus on the realism while also trying not to get violations, you CAN do this, so at the same time it’s good advice :)
But if you’re looking for realism, you shouldn’t follow this. What you CAN do tho, is if you have an aircraft that struggles to slow down, you can put 0% throttle a few minutes before, and if that doesn’t work, adjust your VS descent rate to something higher (trust me on this one) and when you reach your preferred IAS depending on your altitude, than you can descend whatever VS you want (keep in mind you just lowered your speed so it’ll be easier to descend). This works ALL the time for me (specifically on the max cuz it has bad spoilers).
I’d want to address your original post but since you’ve deleted it, I’m not sure if that could be taken as you retracting your statement or if it’s a subtle admission to being misguided by assumptions. That being said, having spent a large portion of my free time gaining knowledge in this area, and having specifically been familiarising myself with the B777 in recent times, I think I am in a position where I can comment on certain statements that you have made. That being said, I want to make it absolutely clear that I am not a B777 type-rated pilot, nor am I a pilot to begin with. Having also made all the clarifications I need to, I am personally friends with people who are active pilots on the B777 for a major carrier in the Middle East, so the statements I am about to make has with it the first-hand experiences of my friends being at the helm of the B777.
On a VNAV descent in any plane for that matter, it is not uncommon to find yourself with a negative attitude or being in a nose-down profile. In the real world, it’s especially common when you’re flying with a light payload and with low fuel, and if you’re also given the clearance for a high speed descent. That being said, this is not completely exclusive to high speed descents, as normal VNAV profile descents could see you with a nose-down attitude in general. As long as the plane is in its window of manoeuvring and the multiple flight-computers in the plane senses that it is not in an unstable condition, a nose-down attitude is completely normal scenario.
This is a very overarching statement and is not true in many scenarios. Through the experience I have on flight simulators and having spoken to many flight crews on flights that I’ve been on, it’s more common to see the speed in cruise be determined through what’s known as the Cost Index value. This is a value that could range from 0 to 500 in Airbus or 0 to 999 in Boeing aircraft.
While this value in itself does not determine the cruise speed that you fly at arbitrarily, it does determine the cruise speed that you fly at for a given gross weight, centre of gravity, altitude and the desired fuel burn, so that a balance could be reached in fuel savings while flying fast enough to reach your destination in a timely manner. The takeaway from Cost Index values in general is that 0 prioritises fuel savings by cruising slower, and a higher cost index prioritises speed at a cost of additional fuel burn.
In the B777, even at a Cost Index of 0 (which I must mention is very rare for airlines to utilise), the B777 could find itself cruising at speeds like Mach 0.81-0.82 at altitudes between FL350 to FL430. Having mentioned that, a cruising speed of Mach 0.81-0.82 wouldn’t necessarily be appropriate in a plane such as the B737 or A320 family, as this is far closer to the Mach limit that these planes could cruise at.
Under normal VNAV descent profiles, you wouldn’t typically slow much more than your cruise speed between your cruise altitude and FL280, unless there is a speed restriction in the STAR that you are flying, or if ATC itself restricts you to a fixed speed. While theoretically possible for ATC to restrict your speed during the descent at all phases, it’s not common to hear a restriction for a speed that low at such high altitudes.
From comments made by my friend about the drag profile in the B777 during descent, having flaps 1 or 5 deployed is not likely to be a decision motivated by wanting increased drag. Rather, this is likely a setting that is used in anticipation of an upcoming descent speed restriction or in preparation for further deceleration where the selection of flaps 15 or 20 would actually induce significantly more drag. However, keep in mind that your spoilers are always an option and it’s also there for a reason; to spoil your lift and induce more drag to slow you down. It’s even in the name.
You would be correct as flaps 5, 15 and 20 are the profiles that are available to flight crews, and generally speaking, lower flap settings are desired as there is less induced drag as you enter the acceleration phase and not having to think about multiple flap retractions is also desired as you’d probably have enough things to think about while climbing out and hitting the cross on your Flight Director.
I have to mention that you would be grossly incorrect in this instance as I think you have a flawed understanding of when the retractions occur in the take-off phase.
After passing the initial climb phase and entering the acceleration phase, which is after hitting your initial climb speed, and being commanded to pitch down to accelerate by your Flight Director to 250 knots, you retract your speed according to the flap retraction marks as would be displayed on your PFD. This speed is determined by the flight computers themselves and will account for multiple factors during that phase of flight so this speed changes from flight to flight.
Personally, on my most recent B777 flight which was a Singapore Airlines B777-300ER from Singapore to London, we took off in conditions that were hot enough and with such a small margin to the maximum take-off weight that the crew was more comfortable with climbing to 10,000 feet with flaps 5 and at 230 knots with a lower angle of attack than retracting flaps to 1 and climbing with a far higher angle of attack at 250 knots to 10,000 feet.
I’ve been on many flights on the B777 too which involved a take off, climb, cruise, descent and landing. I’ve also spoken to multiple flight crews and have a friend who is a pilot on the B777 in the real world too. I think my educated comment holds substance in this context.
Disagreeing on a person’s information and being wrong about a statement that was made are two mutually exclusive conditions. It is possible for a person to disagree with your statement, and for you to be wrong too.
You made a mistake, which was pointed out to you, and an explanation on your mistake was made to you. You assumed that someone called you an ‘unrealistic idiot’ yourself. Ironic.
I didn’t delete it ToasterStroodie flagged it and had it removed. But thank you for you knowledge. The 777s are my favorite aircraft types and alot of my information i got is from research and plane spotting. I typically record them watch the recordings and reviewing the track history through flight rader 24’s playback history for information to apply into my plane spotting videos I make. If i don’t know something I like to try and research the information. Google does tend to be miss guiding so having some information prior is required when researching. I appreciate the information as i love learning things in aviation other than airlines fleet retirement plans.
Except he did attack maybe not meaning to but this part of the text especially and the overall tone behind his message came off to me as an attack not a disagreement.
Thank you for letting me know. If my information is wrong I like to know the right information. My goal is not to give misslead information but give information based on research and observations. Clearly I did go wrong somewhere.
Energy management is a tricky thing to learn, even more so in the real world. It takes pilots around 1000 hours on type, sometimes more, to truly master it.
However, what I would suggest is baring in mind that the VNAV system in IF is not particularly realistic. It doesn’t allow for FMC planned ‘decel’ points like the real aircraft would, so you have to plan your own.
There’s no ‘correct’ way to do this, however I’d suggest using the altitudes given on the arrival plate as a guide line. A good rule of thumb is
3 x change in altitude = distance required for descent, ± 1 mile per 10 knots of speed change.
So for example, say you need to be at FL100 and 250kts at a specific waypoint. If you’re defending at 280 KIAS (a perfectly normal speed for a 737) from FL350 to FL100, 25 x 3 = 75
You also need to lose 30 knots, so +3 miles.
Add in some breathing room, is suggest starting your descent around 80 miles from the waypoint at which you need to be at 250kts.
This is true of all aircraft, just adjust the distances for the aircraft you’re flying. The 777 and A380 are good examples because the drag model is questionable (seemingly broken, in the case of the A380). So instead of 1 mile per 10 knots, perhaps call it 3 or 4 to be on the safe side and go with that. Use VS mode to level out your descent early to allow the aircraft to slow down too, -1000ft per minute is a perfectly normal rate of descent during a decel phase.
Note: I say broken because around 10,000ft the A380 will still struggle to slow with a low rate of descent which I understand to be not particularly realistic.
I was curious so I checked out deceleration at 10K feet, 50% load, and at 1000fpm in clean configuration, I was getting a deceleration of about 1 kt per second (starting just below 250kts IAS).
I did a quick glide ratio calculation using IAS (to remove the density altitude dependence of TAS on distance) against VS, and it came out to about 14.5/1.
I don’t have robust references, so I don’t now with any certainty, but it can’t be too far off one might assume?
If you check IRL cockpit videos (trust me I’ve watched hundreds of them) you’ll notice that they actually start to slow down the plane to 250 knots IAS at around 11,000-15,000 or more feet (DEPENDS on how slippery the aircraft is) because it’s right before you reach 10k feet which obviously the max IAS is 250 at that alt.
IMPORTANT LIFE-CHANGING TIP !!
What I do to specify my Mach speed at different altitudes is using the PDF simbrief gives you after generating a flight plan and it literally gives you the specific mach AND true airspeed (TAS) for EVERY single waypoint (including TOC and TOD) which is so fricking amazing.
Before I found out about simbrief’s PDF, my flight time compared to the real route I was recreating was very inaccurate, but ever since I’ve followed the PDF, it has improved drastically. Example: my flight time from Lisbon to Madeira before I used simbrief was 2 hours exactly, but IRL it’s only like 1h25m so I was completely off. But ever since I’ve followed the simbrief PDF, my Lisbon to Madeira flights have always ranged from 1h20 to 1h30 which is a huge step up for realism.
Hey my friend, it’s been a while! I’m good, how are you?!
Calculations seem fair enough to me - but did you test them using a simulated ‘Flight Idle’ of around 35-37%?
I try to fly as realistically as I can (as you well know from our previous conversations haha!) so use flight idle thrust in descent. In aircraft like the 737, this works out fine and I get a rate of descent comparable to what I expect in the real aircraft.
The same, however, cannot be said for the A380 in IF. That was the reason for my previous statement. I’m not sure if IF shows 20% N1 at idle in flight purely for visuals but simulates a higher flight idle, but I can’t see why it would work that way.
The other thing I’d suggest checking is the deceleration from around 320KIAS down to 250 when descending towards 10,000ft. That’s the main sticking point for me, I find I have to essentially level off completely to get a sensible rate of decel with flight idle thrust.
I was just at throttle zero, without thinking about that tbh. Fair point. The glide ratio of course was done at as close to zero change in IAS as possible (also throttle zero).
Good point. I’ll try that again in a bit.
How’s the flight training going?
Years ago I experienced that irl approaching San Jose. It came as quite a surprise, and the drag impact and expedited descent rate was very unmistakable.
As for the op’s (@Theflyingsouthwest9 ) topic question, as others have mentioned, my first priority would be to emphasize leaving plenty of time for the descent (the “secret ingredient” to energy dissipation is time).
In an ATC pinch, I would also not hesitate to drop the gear, make sure spoilers are out, and reduce the descent rate to the minimum possible to get the speed down.
@BennyBoy_Alpha What would be the criteria for whether an aircraft commanded to a lower altitude is descending fast enough to be compliant with the instruction? Like, what might be the minimum such criteria for judgement?
There isn’t a specific value per se (at least as far as I’m aware) but when acting as a pilot I tend to go between -1000 and -2000fpm - its quick enough to ensure an efficient descent but also not too steep that I’ll find it tricky to slow down. I haven’t had any issues doing that up to this point.
In terms of ATC giving an instruction to descend, if the pilot was descending at 500 fpm or less, or even leveled out for 60 seconds more or less, can that trigger a “not following instructions”?
I guess I’m asking: is there any lower limit for not complying with a descent instruction (say if a pilot drastically, but for a limited time reduces the descent rate, perhaps in combination with gear extension in a rush to dissipate speed/energy)?
Maybe too nitpicky a question(?), but I’ve wondered in the past.
